Efficacy of time restricted eating and resistance training on body composition and mood profiles among young adults with overweight/obesity: a randomized controlled trial

ABSTRACT

Background/Objective

Dietary restriction or exercise regimens can promote weight loss or physical fitness among patients with obesity. However, intervention-associated adverse effects may impede patients’ motivation to participate in dietary/exercise interventions. We examined the effects of time restricted eating (TRE) with or without resistance training (RT) on body composition, mood profile, and sleep quality in young college adults with overweight or obesity.

Methods

Fifty-four young college students with overweight/obesity were randomized into control (CON), TRE, RT, and TRE plus RT (TRE+RT) trials. The TRE trials restricted to an eating window of 10-hour/day for 8-week. The RT trials performed supervised resistance exercise, while the control trial maintained a regular lifestyle. Changes in body composition variables, blood pressure, mood status, and sleep quality were measured before and after the intervention.

Results

TRE intervention alone or in combination with RT significantly (p < 0.01) decreased body weight (>2 kg) and BMI (~1 kg/m²) in adults with overweight/obesity. Both RT alone and combined with TRE substantially decreased fat mass by 1.1 ± 0.5 and 3.2 ± 0.4 kg, respectively. The decreased fat mass was greater in the combination trial than in the RT trial, whereas TRE alone had no effect. In contrast, fat-free mass was significantly (p < 0.01) decreased with TRE (−2.3 ± 06 kg), increased with RT (1.6 ± 0.3 kg), and was stably maintained with combination interventions. The reduced waist and hip circumferences in the TRE (p < 0.01) were similar to those in the TRE+RT trials, however, RT alone had no effect. Time and group interaction showed a large effect size (partial eta squared) for all body composition variables. In addition, RT with or without TRE notably decreased diastolic blood pressure (RT: −5.5 ± 1.9 mmHg, TRE+RT: −4.1 ± 1.5 mmHg, p < 0.05). Mild anxiety levels at baseline in RT (4.8 ± 2.6) and TRE+RT (4.1 ± 3) trials were found to be normal at postintervention in TRE+RT (3.6 ± 1.7) but not in RT (5.6 ± 3.5). No depression or stress was recorded among the participants during the intervention. The reported poor sleep quality among participants at baseline was significantly improved with RT (4.8 ± 2.9; p < 0.05), and tended to improve with TRE+RT interventions (4.5 ± 1.9).

Conclusions

10-hour TRE is beneficial for weight/fat loss without affecting mood status. However, TRE combined with RT might be more effective for weight/fat loss, maintaining muscle mass, and good quality of sleep among young adults with overweight or obesity.

1. Introduction

Overweight and obesity, defined as abnormal or excessive fat accumulation, are the growing public health concerns. The number of people with overweight and obesity is dramatically increasing around the world [1]. According to the World Health Organization (WHO), approximately 2.5 billion adults (18 years and older) are overweight, and 890 million of these adults are obese worldwide [2]. The number of people with obesity is estimated to reach one billion by 2030 [3]. Obesity is a risk factors for developing many noncommunicable diseases, and it may promote disease-related morbidity and mortality. Obesity accounted for approximately 5 million disease-related deaths, including cardiovascular diseases (CVDs), diabetes, neurological disorders, digestive disorders, certain cancers, and chronic respiratory diseases [1,4]. As the leading developing nation, China has experienced a surge in the overweight and obese population in recent decades, which is due to its rapid economic growth, urbanization, and changing lifestyle behaviors [5,6]. China also witnessed substantial changes in dietary patterns, including increased consumption of energy-dense foods and decreased physical activity [7]. Recent findings in 2023 revealed that 34.8% of the overall Chinese population is overweight and 14.1% is obese [8]. The main cause of overweight or obesity is an energy imbalance between intake and expenditure that results from excessive intake of calories, unhealthy eating patterns, sedentary behaviors, or lack of physical activity [9]. The WHO classifies adults as overweight with a body mass index (BMI) of 25 kg/m² or higher, and as obese with a BMI of 30 kg/m² or higher [10]. The Working Group on Obesity in China (WGOC) has recommended that a BMI of 24 to <28 kg/m² as overweight, and a BMI of ≥28 kg/m² as obese [7,11].

Calorie restriction (CR, an intentional restriction) is a nonpharmacological intervention for controlling weight gain and preventing cardiometabolic disorders in adults with overweight and obesity. However, practicing CR (20–40% decrease in daily energy intake) is difficult, and may increase the risk of malnutrition over a period of time [12,13]. Intermittent fasting (IF), an alternative to CR, has gained popularity and has shown similar health benefits in weight management and cardiometabolic parameters [14,15]. IF is an eating pattern that switches between certain periods of eating and refrain from eating [16,17]. Although both CR (intentionally) and IF (unintentionally) restrict the energy intake, IF offers some advantages over CR, in terms of compliance, risk factors, and implementation [12,13]. The most common patterns of IF include time restricted eating (TRE), alternate-day fasting (ADF), 5:2 diet, whole-day fasting (WDF), and periodic fasting [13,18]. Adherence to the protocols like CR (61%) [19] or ADF (78%) [16] is a challenge to participants, however, TRE was reported to have greater adherence (>84%) [16,19], and this can be easily incorporated into daily lifestyles [17]. TRE, a well-tolerated popular strategy, typically restricts the daily eating window (time), which causes an unintentional reduction in caloric intake [17,20]. The eating window in TRE trials ranges from 4- to 10-hour a day, while the remaining hours (14–20) are fasting [21].

Several studies have shown that TRE induces considerable health benefits, including weight loss, blood glucose homeostasis, and metabolic syndrome risk factors [22–25]. However, the beneficial effects of TRE are diverse and depend on the fasting hours and/or health status of individuals. TRE either 4- or 6-hour for 8 weeks induced similar energy reduction (~550 Kcal/day) and similar weight loss (~3%), while loss of lean mass in 6-hour TRE was greater than 4-hour TRE in adults with obesity [25]. Chow et al. reported that an 8-hour eating window can decrease body weight and fat mass but contributes to decrease lean mass in adults with obesity [26]. Schroder et al. reported that 8-hour TRE (3 months) decreased body weight, BMI, fat percentage and waist circumference (WC) in women with obesity, while blood biomarkers of metabolic syndrome remained unchanged [24]. TRE-induced decreases in lean mass could negatively impact body composition in obese individuals [24,26].

TRE combined with exercise has been shown to improve overall health and body composition, but its efficiency relies on the modalities of TRE, exercise, and/or health status of participants [27]. A randomized controlled trial (RCT) reported slightly increased lean mass, and greatly decreased fat mass and total body mass with TRE (8-hour, 8-week) plus aerobic and resistance exercise compared to normal eating plus exercise in adults with overweight and obesity [28]. In contrast, Stratton et. al., reported short-term TRE (8-hour, 4-week) combined with resistance training (RT) did not elicit more beneficial effects on body composition and had no negative impact on fat-free mass compared to a normal diet with RT in the isocaloric state in active males [29]. However, no study has included TRE only and TRE plus exercise groups within the same investigation [28,29]. A recent RCT reported that TRE (≤10-hour) combined with high-intensity intermittent training (HIIT, 7-week) decreased body mass and fat mass, and preserved TRE-induced loss of muscle mass in women with overweight/obesity [30].

Obesity is significantly associated with a range of common mood and anxiety disorders, which may lead to impairing the quality of life of people [31,32]. Intentional weight loss interventions with TRE and exercise are claimed to improve mood disturbances and quality of life, and decrease depressive symptoms in adults with obesity [33–35]. Contrary, TRE for 12-month did not affect depression, mood or quality of life of adults with obesity [36]. Furthermore, the effect of TRE on the sleep quality of participants is reportedly debatable. For instance, 10-hour TRE (16-week) improved sleep quality in adults with overweight [37], while 10-hour TRE (12-week) had no effect in adults with metabolic syndrome [38]. Despite the significant weight loss, exercise combined with ADF did not improve sleep quality or duration in patients with nonalcoholic fatty liver disease [39]. On the other hand, it is claimed that TRE with a 10-hour eating window has high compliance and similar effects like an 8-hour eating window, on various clinical outcomes in patients [38,40]. However, none of the studies addressed the combination effect of 10-hour TRE plus RT on body composition and psychological outcomes (mood swings, sleep quality) in young adults with overweight or obesity. Therefore, in this RCT, we aimed to investigate the independent effects of TRE (10-hour) or RT, as well as the combination effects of TRE plus RT, on changes in body composition variables, blood pressure, mood swings, and sleep quality among adults with overweight and obesity.

2. Methods

2.1. Participants

We recruited physically active overweight and obese college students from Zhejiang Normal University. The average age of the participants was approximately 20 years, and their average BMI was 26 kg/m². According to the WGOC recommendations for the Chinese population, a BMI of 24 to <28 kg/m² is overweight, and a BMI of ≥28 kg/m² is obese [7,11]. Participants with a history of chronic diseases, gastrointestinal abnormalities, hypertension, diabetes mellitus, or using any medications were excluded. In addition, participants who had a history of eating disorders, an eating window less than 10 hours per day, or who were involved in weight loss interventions (dietary or exercise) also excluded. All participants with good health and physical fitness levels voluntarily participated, and written informed consent form obtained before participation. This study design and all protocols were reviewed and approved by the institutional review board of Zhejiang Normal University with the approval number ZSRT2023063.

2.2. Study design

Initially, a total of 58 participants were recruited for this study. All participants were randomized into four groups: control (CON, n = 13), time restricted eating (TRE, n = 16), resistance training (RT, n = 15), and TRE plus RT (TRE+RT, n = 14). Randomization was carried out by a computer-generated sequence random number that ensured each participant had an equal probability of being assigned to any of the trials. The duration of this study was eight weeks. One participant dropped out of the control trial (n = 12) due to the common cold, and one participant from the TRE trial (n = 15) and two participants from the RT trial (n = 13) dropped due to time conflicts with the experimental schedule. Body composition, blood pressure, and questionnaire data collected before (pre-) and after (post-) intervention. Participants in the control trial maintained a regular lifestyle without intense exercise or dietary restrictions. The detailed grouping and number of participants in each trial (Consolidated Standards of Reporting Trials, CONSORT) depicted in Figure 1.

Figure 1.

The CONSORT flowchart of the study design and grouping.

2.3. Time restricted eating

Participants in the TRE and TRE+RT trials strictly practiced daily restricted eating time with an eating window of 10 hours for a period of 8 weeks. Participants were instructed to choose any 10 hour period in a day between 8:00 and 20:00, as their preferred mealtime, and the rest of the time was fasting. During the intervention period, we did not restrict the type, quality, or portion of each meal. However, participants were asked to take a picture of their meal/food each time, and upload it to the laboratory group chat to ensure that they were following their time of eating. During the fasting hours, participants were allowed to drink enough water without restriction. However, other beverages, such as sweetened tea, fruit juices, energy drinks, caffeinated and/or alcoholic drinks, were not permitted. Designated authors from the research team randomly visited or called the participants, and tracked their mealtimes to ensure strict practice and adherence to the TRE protocol. There are no considerable differences in the daily eating window (breakfast, lunch, and dinner) among the participants. Since the eating window starts early, we considered this as early-TRE, but with an extended eating window of 10-hour, known as early 10-hour TRE [21,41].

2.4. Exercise intervention

Participants in the RT and TRE+RT trials performed supervised resistance exercise three times per week for eight weeks. One week prior to the experiment, participants practiced relevant training movements to familiarize themselves with the RT protocol at the university campus gymnasium. All training movements with a number of repetitions were explained and demonstrated by an experienced physical education trainer to ensure adherence. The RT protocol consisted of three nonconsecutive exercises per week. Participants performed total-body workouts during each training session. Each training session was composed of six types of movements, including three upper-body exercises and three lower-body exercises. Each movement was performed in four sets of 8–12 repetitions with a load of at least 60–70% of one repetition maximum (1RM) [42]. The rest interval between sets was 60 to 90 seconds. The total training session lasted 45-min, including a 10-min warm up and a 5-min cool down. The upper-body exercise consisted of a bench press, high pull downs, and dumbbell curls. The lower-body exercise consisted of a leg press, seated leg curls, and leg extension. This training protocol was adopted from the guidelines of the ACSM [43]. Participants were verbally encouraged to perform the required number of repetitions in each set of workouts. The training protocol was scheduled between 4:00 and 6:00 pm on the respective days, and participants were strictly instructed not to consume any pre- or post-exercise protein or energy supplements. Each exercise training session was supervised by a professional physical education trainer to ensure the complete performance of each movement. Upon completion, participants were not allowed to perform for additional time or additional sets of workouts. In addition, the exercise performance of each participant was recorded at the end of the workout in the gymnasium log book.

2.5. Body composition measurement

The body composition of participants from all trials was measured before and after the intervention using a TANITA body composition monitor (Tanita MC-180, Tanita Co, Tokyo, Japan). The measured body composition variables are body weight, fat mass (FM), and fat-free mass (FFM). All assessments were done right before the breakfast under overnight fasting (no food or fluids) to obtain accurate readings. Following body composition, the height of the participants was measured using an electronic measuring instrument (Hengkangjiaye, Shenzhen, China). BMI was calculated by dividing the weight (kg) by the height (m) of the participant and is expressed as kg/m². Next, WC and hip circumference (HC) were recorded using a measuring tape, while the participants were standing to the nearest 0.1 cm.

2.6. Measurement of heart rate and blood pressure

Changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate were assessed before and after the intervention using an Omron electronic sphygmomanometer (Omron, Dalian, China). These assessments were performed by a specialist in a closed room with a pleasant atmosphere. All participants were tested at the same time as possible after stabilizing for at least 10 min before the test. The measurements were performed twice, and the mean values were used as the measurement values.

2.7. Assessment of depression, anxiety and stress

The Depression Anxiety Stress Scale-21 (DASS-21) was used to assess the mood of the participants [44]. This questionnaire contains 21 questions, seven related to stress (e.g. persistent state of overarousal and low frustration tolerance), seven about anxiety (e.g. fear and anticipation of negative events), and seven about depression (e.g. loss of self-esteem/incentives and depressed mood). Each seven-item scale has four response options ranging from 0 (did not apply to me at all) to 3 (applied to me much, or most of the time). The maximum score for each domain (depression, anxiety, and stress) was 21. For depression, a score of 0–4 indicated normal, 5–6 indicated mild depression, 7–10 indicated moderate depression, and 11–21 indicated severe depression. For anxiety, a score of 0–3 indicates normal, 4–5 indicates mild anxiety, 6–7 indicates moderate anxiety, and 8–21 indicates severe anxiety. For stress, a score of 0–7 indicates normal, a score of 8–9 indicates mild stress, a score of 10–12 indicates moderate stress, and a score of 13–21 indicates severe stress. The DASS-21 reported to have high reliability and validity for measuring anxiety, stress, and depression in the population [45].

2.8. Assessment of sleep quality

The Pittsburgh Sleep Quality Inventory (PSQI), a self-report questionnaire, was used to measure the quality and patterns of sleep over eight weeks [46]. The PSQI consists of seven subscales or elements, including sleep latency, subjective sleep quality, sleep duration, sleep disturbances, habitual sleep efficiency, use of sleeping medications, and daytime dysfunction. The score range for each subscale is 0 to 3, and the PSQI total score range is 0 to 21. A score greater than 5 indicates poor sleep quality. The PSQI has adequate content validity and adequate internal consistency [47].

2.9. Statistical analysis

The statistical analysis was performed using IBM Statistics SPSS software (version 26.0 SPSS, Inc., Chicago, IL, USA). Initially, we conducted repeated measures analysis of variance (ANOVA) for the group x time interaction effect. The effect sizes were expressed as partial eta squared (η²). According to the Cohen’s standard, the threshold of effect size is categorized and interpreted as large (η² = 0.14), medium (η² = 0.06), and small (η² = 0.01) [48]. To compare the baseline (pre) values with after intervention (post) values within the groups, we performed paired t-tests. One-way ANOVA was used to compare the group differences (change values), and Tukey’s post hoc test was employed to identify the significant differences. All results with p values less than 0.05 were considered statistically significant. All the results are presented as the means and standard deviations (SDs).

3. Results

3.1. Study participants and baseline characteristics

Young college adults with an average age of 20 years and an average BMI of 26 kg/m² participated in this study. According to the WHO and WGOC classifications for the population in China, all participants in this study were overweight or obese [7,11,49]. As shown in Figure 1, four participants were excluded for various reasons, and 54 participants completed the study protocols. The final number of participants in each trial and their baseline characteristics are presented in Table 1. Anthropometric variables and blood pressure measured at baseline were not different among the trials (Table 1). Participants had three meals a day (breakfast, lunch, and dinner), and the reported daily meal timings were not different between TRE and TRE+RT trials. The average breakfast time was 8:14 AM, and dinner time was 5:50 PM in TRE trials. The targeted daily eating window was achieved in both trials, as shown in Supplementary Table 1.

Table 1.

Baseline characteristics of participants.

Assessments	CON	TRE	RT	TRE+RT
Number	12	15	13	14
Female/male	10/2	9/6	9/4	8/6
Age (years)	20 ± 1	20 ± 1.1	20.2 ± 0.9	21 ± 2
Weight (kg)	71.8 ± 12.8	73.7 ± 8.5	73.5 ± 9	74.2 ± 10
Body mass index (kg/m2)	27.3 ± 3.4	26.3 ± 1.4	26.7 ± 01.6	26.8 ± 1.6
Systolic blood pressure (mmHg)	114.5 ± 4.9	117.3 ± 13.6	115.3 ± 10.8	119.6 ± 7
Diastolic blood pressure (mmHg)	71.9 ± 6.8	73 ± 8.3	74 ± 8.5	74.1 ± 7.4
Heart rate (bpm)	76.6 ± 5.5	74.9 ± 14.7	79.4 ± 12.6	74.8 ± 9.8

CON, control; TRE, time restricted eating; RT, resistance training; TRE+RT, time-restricted fasting plus resistance training; kg/m², kilogram/square meter; mmHg, millimeter of mercury; bpm, beats per minute. The values are expressed as the means ± SD.

3.2. TRE promotes weight loss in young adults with overweight and obesity

In this study, we found that a TRE intervention for 8 weeks significantly decreased body weight (−2.6 ± 0.4 kg, p  < 0.01) in adults who were overweight or obese. This decrease was further indicated by a greater reduction in BMI (−1 ± 0.1 kg/m², p < 0.01) after the TRE intervention (Table 2). Similarly, decreased body weight (−2.9 ± 0.5 kg, p < 0.01) and BMI (−1 ± 0.2 kg/m², p < 0.01) were also observed when TRE was combined with RT. However, 8 weeks of RT alone had no effect on either the body weight or BMI of adults with overweight or obesity (Table 2). The results from repeated measures ANOVA revealed that the time and group have large interaction effects on body weight (F = 15.388, p < 0.000, η² p = 0.48) and BMI (F = 15.505, p  < 0.000, η² p = 0.482) changes among participants (Supplementary Table S2).

Table 2.

Changes in body composition variables in adults with overweight and obesity.

Assessments	CON	TRE	RT	TRE+RT
Body weight (kg)
Pre	71.8 ± 12.8	73.7 ± 8.5	73.5 ± 9	74.2 ± 10
Post	72.2 ± 13.4	71.1 ± 8.6**	73.8 ± 9.3	71.2 ± 9.6**
Change	0.3 ± 1.3	−2.6 ± 1.6##	0.3 ± 2	−2.9 ± 1.7##††
Body mass index (kg/m2)
Pre	27.3 ± 3.4	26.3 ± 1.4	26.7 ± 1.6	26.8 ± 1.6
Post	27.4 ± 3.5	25.3 ± 1.6**	26.8 ± 1.7	25.7 ± 1.7**
Change	0.1 ± 0.5	−1 ± 0.6##	0.1 ± 0.7	−1 ± 0.6##††
Fat mass (kg)
Pre	23.3 ± 4.4	21.1 ± 3.9	24 ± 5.6	22.6 ± 5.8
Post	24.7 ± 6.1	20.8 ± 3.7	22.8 ± 5.8*	19.4 ± 5.9**
Change	1.4 ± 4	−0.3 ± 1.9	−1.1 ± 1.9#	−3.2 ± 1.6##@@†
Fat-free mass (kg)
Pre	49 ± 10.4	52.6 ± 9.9	49.3 ± 10.9	51.6 ± 10.3
Post	47.4 ± 9.6	50.3 ± 9.6**	50.9 ± 10.9**	51.8 ± 10
Change	−1.6 ± 4.1	−2.3 ± 2.2	1.6 ± 1.3##	0.2 ± 1.5@
Waist circumference (cm)
Pre	86.6 ± 7.6	86 ± 3.9	87.1 ± 5.1	88.3 ± 6.3
Post	84.4 ± 9.9	81.4 ± 4.8**	86.6 ± 5.4	84.3 ± 6**
Change	−2.2 ± 4.3	−4.6 ± 2.7	−0.5 ± 2.9	−4 ± 3.6††
Hip circumference (cm)
Pre	105.3 ± 7.2	104.3 ± 3.8	103 ± 3.2	104.7 ± 5.1
Post	104.1 ± 7.4	99.6 ± 3.6**	102.6 ± 3.1	100.2 ± 4.8**
Change	−1.2 ± 3.5	−4.7 ± 2.2##	−0.4 ± 1.8	−4.6 ± 3.2##††
Waist-Hip Ratio (%)
Pre	82.3 ± 4.6	82.9 ± 5.4	84.5 ± 6	84.4 ± 7
Post	81 ± 5.6	82 ± 6.3	84.5 ± 5.9	84.5 ± 7.5
Change	−1.2 ± 4.4	−0.9 ± 3.7	−0.07 ± 3.9	0.1 ± 4.1

CON, control; TRE, time restricted eating; RT, resistance training; TRE+RT, time-restricted fasting plus resistance training; kg/m², kilogram/square meter. The values are expressed as the means ± SD.

*significant difference between pre- and post-intervention values; *p < 0.05, **p < 0.01.

^#significant difference between CON and TRE, RT and TRE+RT, ^#p < 0.05, ^##p < 0.01.

^@significant difference between TRE and TRE+RT, ^@p < 0.05, ^@@p < 0.01.

^†significant difference between RT and TRE+RT, ^†p < 0.05, ^††p < 0.01.

3.3. Independent and combined effects of TRE and RT on fat mass and fat-free mass

Compared with the control trial (24.7 ± 1.7 kg), adults in the RT trial exhibited a significant loss of fat mass (22.8 ± 1.6 kg, p < 0.05) after 8 weeks. Although TRE intervention alone had no effect on fat mass, TRE combined with RT resulted in a notable reduction in fat mass in participants (pre: 22.6 ± 1.6 kg, post: 19.4 ± 1.6 kg, p < 0.01). The decrease in fat mass in the TRE+RT (−3.2 ± 0.4 kg, p < 0.01) was significantly greater than that in the RT alone (−1.1 ± 0.5 kg) (Table 2). The independent effect of TRE on lean body mass appears to be unfavorable, as decreased FFM was found, while the independent effect of RT was beneficial, as we found increased FFM (1.6 ± 0.3 kg, p < 0.01). Interestingly, a TRE-mediated decrease in FFM was not found when TRE was combined with RT in young adults with overweight or obesity (Table 2). The time and group interaction effects were found to be large for fat mass (F = 7.824, p < 0.000, η² p = 0.319) and also for FFM (F = 7.164, p < 0.000, η² p = 0.301) as showed in the Supplementary Table 2.

3.4. TRE decreases waist and hip circumference in young adults with overweight or obesity

TRE intervention significantly decreased waist circumference (−4.6 ± 0.7 cm, p < 0.01) and hip circumference (−4.7 ± 0.6 cm, p < 0.01) among participants (Table 2). TRE+RT also resulted in a significant (p < 0.01) reduction of waist circumference (−4 ± 1 cm) and hip circumference (−4.6 ± 0.8 cm). Nonetheless, RT alone had no impact on either waist or hip circumference. However, the waist-hip ratio of participants was not altered significantly with either independent or combined interventions (Table 2). We found a large interaction effect of time and group for waist circumference (F = 4.097, p = 0.011, η² p = 0.197) and also for hip circumference (F = 9.076, p = 0.000, η² p = 0.353), but not for waist-hip ratio (F = 0.323, p = 0.809, η² p = 0.019) in adults with overweight and obesity (Supplementary Table S2).

3.5. Effect of TRE and RT on blood pressure and heart rate

The changes in the blood pressure and heart rate of the participants were monitored before and after the intervention. We found that RT intervention independently and in combination with TRE significantly (p < 0.05) decreased diastolic blood pressure, with values of −5.5 ± 1.9 and −4.1 ± 1.5 mmHg, respectively (Table 3). Nonetheless, RT, TRE or TRE+RT had no effect on systolic blood pressure or heart rate in young adults who were overweight or had obesity (Table 3). Furthermore, repeated measure ANOVA results showed that the time and group interaction had no effect on systolic blood pressure (F = 0.188, p = 0.904, η² p = 0.011), diastolic blood pressure (F = 0.332, p = 0.802, η² p = 0.02), and heart rate (F = 0.352, p = 0.788, η² p = 0.021) in adults with overweight and obesity (Supplementary Table S3).

Table 3.

Changes in blood pressure and heart rate among adults with overweight and obesity.

Assessments	CON	TRE	RT	TRE+RT
Systolic blood pressure (mmHg)
Pre	114.5 ± 4.9	117.3 ± 13.6	115.3 ± 10.8	119.6 ± 7
Post	111.8 ± 9.6	112.8 ± 12.9	113.4 ± 9.6	115.3 ± 11.2
Change	−2.7 ± 10.5	−4.5 ± 12.1	−1.9 ± 9.5	−4.3 ± 10.5
Diastolic blood pressure (mmHg)
Pre	71.9 ± 6.8	73 ± 8.3	74 ± 8.5	74.1 ± 7.4
Post	69.3 ± 9.3	70.2 ± 6.2	68.5 ± 6.4*	70.1 ± 8.6*
Change	−2.6 ± 10.5	−2.8 ± 9.6	−5.5 ± 7	−4.1 ± 5.5
Heart rate (bpm)
Pre	76.6 ± 5.5	74.9 ± 14.7	79.4 ± 12.6	74.8 ± 9.8
Post	77.5 ± 6.1	75.5 ± 7.3	76.5 ± 11.3	74.9 ± 11.3
Change	0.9 ± 6.1	0.6 ± 15.5	−2.8 ± 7.3	0.1 ± 9.1

CON, control; TRE, time restricted eating; RT, resistance training; TRE+RT, time-restricted fasting plus resistance training; mmHg, millimeter of mercury; bpm, beats per minute. The values are.

expressed as the means ± SD.

*: significant difference between pre- and post-intervention values within groups, *: p < 0.05.

3.6. Influence of TRE and RT interventions on the mood and sleep quality of participants

To determine the mood swings of the participants, we assessed depression, anxiety, and stress levels before and after the intervention using the DASS-21. We found that TRE, RT, and TRE+RT had no effect on depression or stress levels in adults with overweight or obesity (Table 4). Interestingly, the baseline anxiety scores of overweight and obese young adults were slightly greater than the normal range in the control (4.9 ± 0.8), RT (4.8 ± 0.7), and TRE+RT (4.1 ± 0.8) trials. These mild anxiety levels persisted until the end of the intervention in the control (4 ± 0.9) and RT (5.6 ± 1) trials but not in the TRE+RT (3.6 ± 0.5) trial. The anxiety scores in the TRE trial were reported to be within the normal range at pre- and postintervention (Table 4). In addition, no time and group interaction effects were found for the score of depression (F = 0.159, p = 0.923, η² p = 0.009), anxiety (F = 1.215, p = 0.314, η² p = 0.068), and stress (F = 0.293, p = 0.83, η² p = 0.017) (Supplementary Table S4).

Table 4.

Changes in mood and sleep quality among participants.

Assessments	CON	TRE	RT	TRE+RT
Depression
Pre	2.8 ± 2.6	2.1 ± 2.4	3 ± 2.6	2.9 ± 3
Post	3 ± 1.4	1.9 ± 1.6	2.9 ± 1.1	3.1 ± 2.2
Anxiety
Pre	4.9 ± 2.8	3.6 ± 2.7	4.8 ± 2.6	4.1 ± 3
Post	4 ± 3	3 ± 1.6	5.6 ± 3.5	3.6 ± 1.7
Stress
Pre	5.5 ± 2.2	4.2 ± 2.9	5.3 ± 3.6	4.1 ± 3.3
Post	5.8 ± 4	3.5 ± 2.8	5.6 ± 3.6	4 ± 3
Sleep quality
Pre	6.3 ± 1.6	5.2 ± 2.2	6.8 ± 3.2	5.4 ± 2.4
Post	6.1 ± 2.2	5.3 ± 2.6	4.8 ± 2.9*	4.5 ± 1.9

CON, control; TRE, time restricted eating; RT, resistance training; TRE+RT, time-restricted fasting plus resistance training. The values are expressed as the means ± SD.

*: significant difference between pre- and postintervention values within groups, *: p < 0.05.

Depression scores: 0–4, normal; 5–6, mild; 7–10, moderate; and 11–21, severe. Anxiety scores: 0–3.

normal; 4–5, mild; 6–7, moderate; and 8–21, severe. Stress scores: 0–7, normal; 8–9, mild; 10–12.

moderate; and 13–21, severe. Sleep scores: A sleep score greater than 5 indicates poor sleep quality.

Next, we determined the sleep quality of participants using the PSQI scale, in which a score of five or above indicates poor sleep quality. The baseline sleep scores of participants were reported to be more than five in all trials, including the control, TRE, RT, and TRE+RT trials. These scores revealed that young adults with overweight or obesity tend to have poor sleep quality at baseline. However, sleep quality in the RT trial was significantly improved after intervention (p < 0.05), and an improvement tendency was observed in the TRE combined with RT trial but not in the TRE trial (Table 4). For the sleep quality, we found no time and group interaction effect in our study (F = 2.122, p = 0.109, η² p = 0.113) (Supplementary Table S4).

4. Discussion

The major finding of this study is that TRE and TRE+RT contributed to weight loss and subsequent reductions in BMI in physically active young adults with overweight/obesity. RT intervention alone contributed to decrease fat mass, and this decrease was greater when RT was combined with TRE. In contrast, TRE alone had no effect on fat mass reduction. Fat-free mass, the key body composition variable was decreased with TRE but increased with RT alone. Interestingly, TRE-induced loss of FFM was restored when TRE combined with RT. On the other hand, RT alone had no effect on waist or hip circumference, but TRE and TRE+RT decreased waist and hip sizes. The diastolic blood pressure significantly decreased with RT and TRE+RT interventions. The reported mild anxiety levels at baseline tended to be normal after TRE+RT intervention but not after RT. The poor sleep quality among overweight and obese participants improved only after RT and not after TRE or TRE+RT interventions.

Weight management is crucial, especially in adults with overweight and obesity to prevent the risk of developing CVDs or other metabolic disorders [24]. A reduction in body weight and BMI has been associated with decreased risk factors for CVD in adults with overweight and obesity [50,51]. One of the important findings in our study was that early 10-hour TRE alone, and in combination with RT decreased body weight and BMI. Calorie restriction combined with exercise also contributes to decreased body weight and BMI in adults with overweight and obesity [52]; however, CR may cause adverse effects on metabolic profiles [53]. A recent study reported that either 4- or 6-hour TRE reduced daily caloric intake (~550 Kcal) and decreased body weight (~3%) in adults with obesity [25]. Similarly, a combination of ≤ 10-hour TRE with HIIT decreased body weight in women with overweight/obesity [30]. However, these studies did not compare the independent effects of TRE or RT with a combination effect on body weight or BMI in overweight and obese young adults. According to the WGOC guidelines for the Chinese population, individuals with BMIs ≥ 24 and ≥28 kg/m² are considered overweight and obese, respectively [7,11]. In our study, the reduction of BMI by 1 kg/m² with TRE interventions, but not with RT, emphasizes the nonpharmacological importance of controlling the daily eating window. It has been stated that a meaningful decrease in body weight (3–5%) is clinically important for various health outcomes in overweight and obese individuals [54]. Therefore, a 3.5 and 4.2% weight loss in our study with TRE and TRE+RT, respectively signifies the clinical importance of eating window and exercise for weight management among adults with overweight/obesity. The decreased body weight and BMI with TRE or TRE+RT may be due to reduced energy intake and/or decreased fat deposition [25,55]. Although TRE trials witnessed a greater weight loss rather than exercise, the beneficial effect of RT on the other body composition variables cannot be ruled out, especially in the population with overweight and obesity.

Fat accumulation is a typical phenomenon in overweight or obese condition. Lifestyle modifications, including physical activity and eating behavior, are vital for controlling fat deposition [56]. We found that RT with or without a controlled eating window decreased fat mass in young adults with overweight and obesity. The decreased fat mass with a combination of TRE plus RT was greater than RT alone. A previous study reported that CR alone or combined with exercise also contributed to decrease fat mass in adults with overweight [57]. RT is also known to mobilize visceral fat in adults with overweight and obesity, which may contribute to decrease fat mass [54]. Exercise under fasting or low caloric conditions may promote the utilization of free fatty acids and increase the activities of lipolytic enzymes, thereby enhancing the release of fat from the adipose tissue [58]. An RCT showed dietary restriction alone and also in combination with RT decreased fat mass in overweight men [59]. Contrary, time restricted diet alone in our study had no effect on fat mass, however decreased in the presence of RT. Similar to our findings, Oh et. al. showed that alternate day CR had no effect on fat mass but decreased in the presence of exercise in adults with overweight and obesity [52]. Another RCT reported unchanged fat mass with TRE alone, while significant weight loss and decreased lean mass were reported in adults with overweight and obesity. This study further addressed that TRE-induced weight loss was primarily due to the loss of lean body mass [60]. The latest meta-analysis concluded that the reduction of fat mass with TRE in adults with overweight and obese is associated with the duration of eating window and/or intervention strategies [61]. Nevertheless, the effective weight loss with TRE in our study might be associated with the reduction of fat-free mass rather than the reduction of fat mass.

Fat-free mass refers to the weight of body components other than fat, which is mainly composed of skeletal muscle, and is an important factor that influences metabolism and physical activity [62]. As a highly metabolically active tissue, a reduction in FFM or lean mass not only compromises physical and metabolic health but also increases the risk of developing insulin resistance or type 2 diabetes in overweight and obese adults [63,64]. The TRE-induced loss of FFM in our study might not be associated with prolonged fasting hours (>14-hour), because longer fasting hours (16- and 24-hour) had no impact on muscle protein synthesis or breakdown [65,66]. TRE, regardless of fasting or feeding hours can decrease daily energy intake [17,25]. It is possible to see decreased FFM or lean mass when daily caloric intake is reduced either by restricting the energy intake [59] or eating window [25,26]. During TRE practice, lack of adequate protein intake or exercise that are essential for maintaining FFM might be reasonable for loss of FFM. To support this, RT combined with TRE in our study attenuated TRE-induced FFM loss and maintained stable weight. Similar to our findings, a combination of aerobic exercise and heavy RT reported to preserve the FFM against hypocaloric diet (~1449 Kcal)-induced loss in men with overweight [59]. Contrary, Oh et al. reported that alternate day CR combined with aerobic and RT was unable to maintain muscle mass in adults with overweight and obesity [52]. HIIT combined with ≤ 10-hour TRE was advantageous to preserve muscle mass in women with overweight/obesity [30]. On the other hand, 8-hour TRE combined with RT does not negatively influence the ability to maintain FFM in a hypocaloric state (~1940 Kcal) when sufficient protein (1.83 g/kg) was supplemented [29]. These results suggest that RT in a hypocaloric state like TRE may preserve the FFM, while promoting fat mass loss. Therefore, during TRE, it is necessary to include an adequate amount of protein and/or exercise regimen to maximize the beneficial effects and/or to avoid the possible loss of muscle mass.

It is well known that WC is an indicator of visceral adiposity and a valid predictor of morbidity and mortality. Treatments that decrease WC are important for reducing disease-related risk factors among men and women [14]. In our study, TRE with or without RT notably decreased the waist and hip circumferences of overweight and obese young adults, which emphasizes the clinical significance of TRE. A 3-month TRE trial of obese women reported a significant decrease in WC [24]. Decreased waist and hip circumference following TRE was probably due to reduced fat mass and body weight [24]. TRE and TRE+RT are beneficial for reducing waist and hip circumference in overweight and obese adults, irrespective of RT. One study showed that alternate day fasting combined with exercise can decrease WC and fat mass in obese people [67]. Evidence from a meta-analysis showed that aerobic exercise training is more effective than RT for decreasing WC and body weight, while RT is more effective than aerobic exercise for improving lean body mass in adults with overweight and obesity [68]. The RT intensity or duration in our study might not have been sufficient to decrease WC and body weight; however, it was sufficient to decrease fat mass and increase fat-free mass. Nevertheless, the combination of TRE+RT is effective at reducing the WC and HC as well as body weight and fat mass in physically active young adults with overweight and obesity.

Dietary patterns such as IF and TRE, have shown positive effects on the cardiovascular system, including enhanced parasympathetic activity in the autonomic neurons that innervate the heart and arteries, resulting in a reduced heart rate and blood pressure [69,70]. We found that TRE and RT had no effect on the SBP or heart rate of the participants. The baseline SBP and heart rate values of most participants in our study were within the normal range, which means that our participants were metabolically healthy. Blood pressure values among obese adults with stable physiological and metabolic health remain relatively unaffected by TRE or other dietary regimens [71,72]. In contrast to our findings, 8-hour TRE (12 weeks) decreased SBP without changing DBP or other metabolic variables in adults with obesity [40]. In addition, both types of exercise programs were shown to decrease SBP and DBP in obese adults, and a greater extent of decrease was observed in patients with hypertension [73]. Interestingly, both RT intervention alone (5.5 mmHg) and combined with TRE (4 mmHg) decreased DBP in young adults with overweight and obesity. Similar to our findings, Bermudes et al. also reported decreased DBP but not SBP after aerobic exercise in normal people [74]. Since a reduction in DBP of 5 mmHg is associated with decreased stroke mortality (40%) and ischemic heart disease/vascular mortality (30%) in middle-aged adults [75], decreased DBP with RT and TRE+RT emphasizes the clinical significance of these interventions in overweight and obese young adults. Exercise can decrease adiposity and increase lean mass, which promotes metabolic and endocrine profiles and thereby contributes to controlling blood pressure in overweight or obese people [73].

Depression, anxiety, and stress are the key variables for determining the mood of an individual [76]. Obesity is typically associated with mood disorders and depression, which may lead to poor quality of life [31,32,77]. Weight loss programs, particularly dietary interventions, have been shown to decrease depression symptoms and improve the quality of life in people with obesity [35]. Our findings showed that the depression and stress levels of young adults with overweight/obese were normal at baseline and after the intervention. However, baseline anxiety levels were slightly higher, indicating a mild anxiety state among participants, and this was not observed in TRE trials after 8 weeks. Notably, TRE or TRE+RT did not negatively impact the mood of the participants. Similarly, Fagundes et al. reported that TRE did not affect behavioral parameters (depression, anxiety, and stress) but promoted weight loss in adults with overweight or obesity [78]. In contrast, a study showed that greater weight loss in obese adults after early-TRE with CR was accompanied by improved total mood disturbances and depression but had no effect on sleep quality [34].

The sleep quality of young adults with overweight and obesity was reported to be poor at baseline, and an improving tendency was observed after RT and TRE+RT interventions. TRE alone did not influence the sleep quality of participants, but the physiological reasons for this remain to be investigated. Similar to our findings, Gabel et al. and Wilkinson et al. also reported no change in sleep quality after TRE intervention, regardless of a noticeable (3%) weight loss [38,40]. We assume that a greater degree of weight loss with TRE may contribute to a significant improvement in sleep quality. It has been shown that at least 5% weight loss may be necessary to observe considerable changes in sleep quality among obese individuals [79]. As a nonpharmacological treatment, exercise training is a promising strategy for improving the sleep quality of individuals [80]. In line with this, 8 weeks of RT with or without TRE in our study improved the overall sleep quality of young adults. Although we do not have direct evidence to explain the reasons for improved sleep quality, satisfactory feelings and an overall improvement in quality of life from participants’ feedback may explain the beneficial effect of RT [81,82].

4.1. Limitations

Although our findings are interesting and applicable, especially for young adults who are overweight or obese, there are a few limitations. The sample size in our study was relatively small, and large-scale studies may offer additional evidence. Our study is unable to explain biochemical reasons for changes in body composition variables due to a lack of blood marker data. Despite strict monitoring of dietary compliance, possible deviation in daily eating window or differences in energy intake within the eating window cannot be ruled out among young participants. Although the meal timing of participants was firmly tracked through uploading the meal pictures to laboratory group chat and phone calls, pictures that were taken at different times than their actual meal time and unavailability to answer the phone call might be the possible compliance issue. We assume that controlling of daily eating window and/or decreased energy intake due to TRE might have contributed to altering the FM or FFM in adults. However, calorie intake, macronutrients, and protein intake data were not recorded in this study. Therefore, we are unable to emphasize the decreased protein intake in TRE trials, which is assumed to be a key component in altering the FFM. Furthermore, assessment of body composition with a 2-compartment model rather than a 4-compartment model might be another limitation in our study.

5. Conclusions

Our findings demonstrated that 10-h TRE combined with RT is effective in promoting weight loss among young college adults with overweight or obesity. The beneficial effects were evidenced by greater decreases in body weight, BMI, fat mass, WC, and HC in the TRE+RT trial. The beneficial effects of TRE combined with or without RT on blood pressure, anxiety, and sleep quality were also observed in young adults who were overweight or obese. Our findings suggest that TRE combined with exercise might be effective for weight loss and maintaining muscle mass without affecting mood profile and sleep quality in young adults with overweight/obesity.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

T.C., Y.S. Y.L. and M.K. conceptualized the study. T.C. and Y.S. performed the experiments and analyzed the data. T.C., Y.S., Y.L. and M.K. validated and finalized the data. Y.L., W.Y. and M.K. supervised the study. T.C., Y.S. and Y.L. drafted the original version of the manuscript. W.Y. and M.K. reviewed, revised and finalized the manuscript. All authors have read and approved the final version of the manuscript.

Data availability statement

The data included in this study are available upon reasonable request.

Ethical statement

This study design and all protocols were reviewed and approved by the institutional review board of Zhejiang Normal University with the approval number ZSRT2023063.

Supplementary Material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/15502783.2025.2481127