Effect of intermittent fasting 16:8 and 14:10 compared with control‐group on weight reduction and metabolic outcomes in obesity with type 2 diabetes patients: A randomized controlled trial

ABSTRACT

Aims/Introduction

To compare the percent weight change and metabolic outcomes among diabetic participants with obesity on intermittent fasting (IF) 16:8, IF 14:10, or normal controlled diets.

Materials and Methods

A randomized controlled trial was conducted to randomize participants into three groups. Each group followed IF 16:8, IF 14:10, according to the protocol 3 days/week for 3 months or a control group.

Results

A total of 99 participants completed the study. The percentage weight change from baseline was −4.02% (95% CI, −4.40 to −3.64) in IF 16:8, −3.15% (95% CI, −3.41 to −2.89) in IF 14:10, and −0.55% (95% CI, −1.05 to −0.05) in the control group. The percentage weight loss from baseline was significantly more in both IF groups (P < 0.001, both) when compared with the control group. Weight loss was significantly more in the IF 16:8 group than in that of the IF 14:10 group (P < 0.001). Metabolic outcomes (decrease in FBS and HbA1C, and improvement in lipid profiles) were significantly improved from baseline in both IF groups in comparison with the control group.

Conclusions

Either IF 16:8 or 14:10 had a benefit in the percentage weight change, glucose and lipid profiles in obese diabetic patients compared with the control group when consumed for 3 days a week for 3 months.

Either IF 16:8 or 14:10 had a benefit in percent weight change, glucose and lipid profiles in obese, diabetic patients compared with the control group when consumed 3 days a week for 3 months.

INTRODUCTION

Energy intake that is more than energy output can cause obesity. Obesity affects the development of a range of comorbidities, including type 2 diabetes mellitus, hypertension, dyslipidemia, cardiovascular disease, certain types of cancer, and an increased mortality rate ¹ . The definition of obesity in Thailand uses the Regional Office for the Western Pacific (WPRO) criteria which classifies overweight as a body mass index (BMI) of 23.0–24.9 kg/m², Class I obesity as a BMI of 25.0–29.9 kg/m², and Class II obesity as a BMI of ≥ 30.0 kg/m^{2 2} . The treatment of obesity consists of lifestyle modification through diet control and exercise, anti‐obesity drugs, and bariatric surgery. The choice of treatment depends on underlying disease, severity of obesity, contraindications, and the indications of each treatment options ³ . Intermittent fasting (IF) has been used popularly in diet control for weight loss. It consists of regular alternating periods of unrestricted dietary consumption and abstinence from caloric intake. Intermittent fasting has the benefit of decreasing weight, controlling blood pressure, and reducing the risk of metabolic syndrome ⁴ , ⁵ , ⁶ , ⁷ .

There are several popular types of intermittent fasting, such as time‐restricted eating (TRE), complete alternate day fasting, and religious fasting ⁸ . In TRE, the daily caloric intake is limited to a consistent window of about 8–10 h ⁹ . 16:8 is a fasting period of 16 h and an eating period of 8 h and 14:10 is a fasting period of 14 h and an eating period of 10 h. Peeke et al. studied TRE 14:10, a subtype of IF for at least 5 days a week for 2 months in non‐diabetic participants with a BMI of ≥ 30.0 kg/m² and found that TRE 14:10 helped them to lose 8.5% of the baseline body weight (P < 0.001) and significantly decreased blood glucose by 7.6 mg/dL from the baseline (P < 0.05) ¹⁰ . On the contrary, the study of Lowe et al. in non‐diabetes with a BMI of ≥ 27 kg/m² using TRE 16:8 resulted in a decrease of body weight (BW) when compared with the baseline (−0.94 kg; P = 0.01), but was not statistically significant when compared with consistent meal timing ¹¹ . Nowadays, there is a gap in knowledge about the difference in weight loss and metabolic outcomes in types of IF. The previous study showed that 10 h restricted feeding improved blood glucose and decreased the BW when compared with the control ¹² . However, there are no previous data comparing two IF groups and a control group for weight loss and metabolic outcomes. Therefore, the purpose of this study was to investigate the effect of IF 14:10 and IF 16:8 on weight reduction and metabolic outcomes in obese diabetic patients when compared with control or a normal diet. We would like to compare two IF groups to see whether there is any difference in outcomes between fasting for 16 and 14 h. If fasting for 14 h has the same benefit as fasting for 16 h, we might suggest that our diabetic subjects fast only 14 h as it is easier to follow. The primary outcome was weight loss. The secondary outcomes were changes in fasting blood glucose (FBS), HbA1C, and lipid profiles.

MATERIALS AND METHODS

Study design, setting

This 12 week RCT was carried out in the Outpatient Clinic at the Faculty of Medicine, Chiang Mai University Hospital, Chiang Mai, Thailand from 23 November 2021 to 30 September 2022. This study was conducted following the Declaration of Helsinki and was approved by the Research Ethics Committee on Human Rights Related to Research Involving Human Subjects, Chiang Mai University, Thailand (MED‐2564‐08471). Overall, 108 obese participants with type 2 diabetes mellitus, of both sexes, aged 30–60 years voluntarily participated in this research after giving informed consent at a screening visit and were enrolled in the study. The subjects were randomized into three groups, IF 16:8, IF 14:10, or the control group by using 6‐block randomization. Neither the investigators nor the participants were blinded to the intervention. However, the analysis process was blinded to the intervention group. Hypoglycemic agents and lipid‐lowering drugs had to be used in a stable dose during the study except when the participants had hypoglycemia (capillary blood glucose < 70 mg/dL). On a fasting day, if the participants were taking hypoglycemic agents at a once daily dose, the hypoglycemic agents were taken at the first meal. If taking twice a day, the hypoglycemic agents were taken at the first and last meals. If taking three times a day, the hypoglycemic agents were taken at the first meal, in the middle period of fasting, and at the last meal. The IF 16:8 group was instructed to fast for 16 h and the IF 14:10 group fasted for 14 h 3 days per week, 2 days on a weekday, and 1 day on a weekend for 3 months, because it is easy to adhere to the protocol. The participants could drink water during the fasting period. For the control group, the participants ate consistently three meals on diabetic diets. All participants were advised to follow a general diabetic diet (such as avoiding desserts, sticky rice, and high‐sugar diets) advised by a nutritionist and were suggested to exercise at least 3 days per week. The follow‐up required three face‐to‐face visits at 0, 6, and 12 weeks, and one phone visit at 2 weeks. Twenty‐four‐hour food records for 3 and 7 days physical activity records were requested from all groups before each visit. At the first visit, the participants were interviewed face‐to‐face and demographic data including age, underlying diseases, duration of diabetes, current medications, history of complications of diabetes such as diabetic retinopathy and nephropathy, history of steroid use or hormonal drug use, history of hypoglycemia, or history of admission were reviewed from medical records. Anthropometric measurements such as BW, height, weight circumference (WC), and hip circumference (HC) were measured at 0, 6, and 12 weeks. The participants were interviewed about fasting time and eating time, food intake, and hypoglycemic symptoms by phone visit at 2 weeks, and face‐to‐face at 6 and 12 weeks. Fasting blood sugar and lipid profiles were measured at 0 and 12 weeks. The adherence to the fasting time was evaluated from the interview of food intake and food records before each visit. A discontinuation of intervention was evaluated at visits 2, 6, and 12 weeks and was defined as fasting for less than 3 days/week. The hunger score was measured at 6 and 12 weeks. All adverse effects were measured at 2, 6, and 12 weeks. The participants were interviewed regarding hypoglycemic symptoms at all visits.

Participants

The inclusion criteria included all of the following: BMI ≥ 25 kg/m², age 30–60 years old, and type 2 diabetes mellitus diagnosed using American Diabetes Association criteria ¹³ . The exclusion criteria included a history of steroids, hormonal drugs, or weight loss medications used within 3 months, pregnancy or planning to become pregnant, history of cancer, HIV, active pulmonary tuberculosis, hepatitis B or C infection, admission to hospital within 3 months, previous IF in 3 months, previous history of severe hypoglycemia within 6 months, being bed‐ridden, a history of a swallowing problem, GI surgery e.g. bariatric surgery, using insulin injections in the current treatment, glipizide dose >15 mg/day, gliclazide modified release >60 mg/day, taking another sulfonylurea except for glipizide and gliclazide modified release, taking a stable dose of SGLT2/GLP1‐RA for less than 1 month, chronic kidney disease stage IIIB‐V, acute myocardial infarction or stroke within the past 6 months.

Anthropometric measurements

Body weight and height were measured with participants wearing light clothing in a standing position and barefoot with an electronic digital scale Tanita RD‐953 and a stadiometer. Body weight was recorded to the nearest 0.05 kg and height was recorded to the nearest 0.5 cm. BMI was calculated by BW (kg) divided by height squared (m²).

Total calorie intakes and physical activity

The total calorie intake was interpreted from the mean of food records 3 days before each visit. The food records included the amount, meal, timing of eating, and name of foods. The food records were reviewed by phone at 2 weeks and face‐to‐face at visits 6 and 12 weeks. The NutriFact Program, which was developed by Research Institute for Health Sciences, Chiang Mai University, was used for interpreting food intakes. It can interpret the amount and name of food intake to kilocalorie intake by using data from previous research on kilocalories of foods and the nutrient labels on foods in Thailand ¹⁴ , ¹⁵ . The mean of 3 days of food records (kcal/day) at 2, 6, and 12 weeks was calculated. The kilocalories of physical activity (kcal/day) were calculated from weekly physical activity records and regular activities before each visit by using the metabolic equivalent score (MET), duration of activity, age, and BW ¹⁶ , ¹⁷ .

$$\mathrm{\text{The total physical activity}}(\mathrm{kcal}/\mathrm{day}) = \left[\mathrm{activity} ‐ \text{specific MET}\left(\mathrm{kcal}/\mathrm{kg}/\mathrm{h}\right) \times \mathrm{BW} \left(\mathrm{kg}\right) \times \text{duration of activity}\left(\mathrm{minute}/60\right) \times \mathrm{frequency}/\mathrm{week}\left(\mathrm{times}/\mathrm{week}\right)\right]/7$$

Laboratory measurement

After fasting for 8–12 h, venous blood was collected in the morning for measuring FBS, HbA1C, and lipid profiles at 0 and 12 weeks.

Hunger score and adverse effects

The hunger score was a subjective rating and was taken from a visual analog scale, numeric range from 0 to 10, where 0 was the lowest hunger and 10 was the maximum hunger ¹⁸ , ¹⁹ . It was measured by interviewing the participants face‐to‐face at 6 and 12 weeks and recorded to the nearest 0.5. The hunger score was used to evaluate the hunger degree in the morning. The hypoglycemic symptoms were reviewed at all visits. The symptoms of adverse effects were screened with open questions, as well as the frequency of adverse effects such as palpitations, dizziness, headache, abdominal pain, mood change, vomiting, and hypoglycemia.

Statistical analysis

The sample size (N) was calculated by the estimated sample size for two‐sample comparison with repeated measures. A one‐sided, alpha‐error 0.05, a statistical power 80%, ratio = 1:1, with a mean difference of 2.0 kg and standard deviation of 4.5 kg was used from the Peeke et al. study ¹⁰ . The study size was 32 subjects per group. With an allowance of a 10% loss to follow‐up rate, it finally summed with 36 subjects per group, or a total 108 subjects. Statistical analysis was performed using SPSS version 22 and STATA program version 17. Quantitative variables were described as mean ± SD for normally distributed data. Categorical variables were expressed as percentages and frequencies. One‐way ANOVA  was used for continuous variables. The chi‐square or Fisher's exact test was used for categorical variables as appropriate. Changes from baseline were the differences between pre‐intervention and post‐intervention analyzed by using a repeated measured mixed model controlled by baseline data. The percent BW loss was analyzed by using Firth's logistic regression without covariates. The data significant were considered when the P‐value was < 0.05.

RESULTS

In total 109 participants met the eligibility criteria and 108 were enrolled in the study. However, 9 of those were discontinued from the study, 33 participants in IF 16:8 and 33 participants in IF 14:10, who fasted on 3 days/week for 3 months and 33 participants in the control group. Overall discontinuation of intervention and loss to follow‐up was 8.33% as shown in Figure 1.

Figure 1.

Study flow.

Characteristics of the participants at baseline

As shown in Table 1, 99 participants had a mean age of 45.29 ± 6.08 years, mean weight of 82.32 ± 15.37 kg, mean BMI of 31.91 ± 5.16 kg/m², mean type 2 diabetes mellitus duration of 5.42 ± 4.46 years, mean FBS of 149.32 ± 36.92 mg/dL, mean HbA1C of 7.75 ± 0.83%. Most participants were female. There were no significant differences in baseline characteristics among the three groups.

Table 1.

Characteristics of the participants at baseline

Characteristics	IF 16:8 n = 33	IF 14:10 n = 33	Control n = 33	P‐value
Age (years)	46.43 ± 5.89	45.13 ± 6.65	44.32 ± 5.65	0.366
Female sex, n (%)	20 (60.60)	20 (60.60)	18 (54.55)	0.847
BW (kg)	82.31 ± 16.06	81.83 ± 15.50	82.82 ± 15.36	0.967
Height (m)	1.60 ± 0.09	1.61 ± 0.07	1.60 ± 0.08	0.814
BMI (kg/m2)	31.87 ± 4.89	31.45 ± 5.26	32.42 ± 5.42	0.749
WC (cm)	103.84 ± 11.10	104.12 ± 11.01	106.52 ± 10.38	0.547
HC (cm)	104.81 ± 9.42	106.51 ± 11.54	108.11 ± 10.14	0.438
Duration of DM (years)	5.09 ± 4.79	5.52 ± 4.03	5.63 ± 4.63	0.878
Diabetic retinopathy, n (%)	3 (9.09)	5 (15.15)	5 (15.15)	0.702
Urine microalbumin to creatinine ratio, n (%)
<30	22 (66.67)	23 (69.70)	23 (69.70)	0.954
30–300	11 (33.33)	9 (27.27)	9 (27.27)	0.823
>300	0 (0.00)	1 (3.03)	1 (3.03)	1.000
No DM medication	1 (3.03)	3 (9.09)	2 (6.06)	0.869
Metformin, n (%)	32 (96.96)	30 (90.91)	30 (90.91)	0.693
Sulfonylurea, n (%)	11 (33.33)	14 (42.42)	13 (39.39)	0.742
Thiazolidinedione, n (%)	13 (39.39)	10 (30.30)	10 (30.30)	0.664
SGLT2 inhibitors*, n (%)	7 (21.21)	5 (15.15)	7 (21.21)	0.771
DPP4 inhibitors, n (%)	7 (21.21)	5 (15.15)	5 (15.15)	0.753
Dyslipidemia, n (%)	23 (69.7)	25 (75.76)	22 (66.67)	0.711
Hypertension, n (%)	23 (69.7)	22 (66.67)	27 (81.82)	0.343
SBP (mmHg)	135.03 ± 9.42	132.82 ± 9.48	135.82 ± 9.64	0.417
DBP (mmHg)	84.24 ± 7.99	83.21 ± 9.27	82.76 ± 9.06	0.782
FBS (mg/dL)	152.79 ± 35.49	154.79 ± 36.03	140.39 ± 38.62	0.231
HbA1C (%)	7.91 ± 0.94	7.85 ± 0.78	7.49 ± 0.72	0.082
Cholesterol (mg/dL)	185.21 ± 36.64	171.03 ± 33.68	168.78 ± 30.70	0.106
TG (mg/dL)	149.54 ± 51.66	154.65 ± 53.67	170.63 ± 62.76	0.287
HDL (mg/dL)	46.42 ± 9.24	48.21 ± 9.84	44.61 ± 11.12	0.353
LDL (mg/dL)	114.42 ± 33.02	106.06 ± 27.75	98.76 ± 23.22	0.143

Statistically significant at P‐value < 0.05. BMI, body mass index; BW, body weight; DBP, diastolic blood pressure; DM, diabetes mellitus; FBS, fasting blood sugar; HbA1C, hemoglobin A1C; HC, hip circumference; HDL, high density lipoprotein; LDL, low density lipoprotein; SBP, systolic blood pressure; TG, triglyceride; WC, waist circumference.

^*Start taking SGLT2 inhibitor >1 month and stable dose in 1 month when enrolled to the study.

Average total calorie intakes and physical activity

The average total calorie intakes were lowest in all groups at 2 weeks, then the subjects gradually increased their calorie intake at 6 weeks and at the highest calorie intake at 12 weeks. The total calorie intakes in the two IF groups were significantly lower than the control group at 6 weeks, but not at 12 weeks (Figure 2a). There was no significant difference in physical activities among the three groups at any time. The participants in all three groups increased their physical activity in the first 6 weeks as advised, however, it decreased thereafter (Figure 2b).

Figure 2.

(a) Average total calories intake (kcal/day), (b) Physical activity (kcal/day).

BW change from baseline

The percentage of weight change at 6 and 12 weeks in the control group was not significantly different from the baseline. Both the IF groups had a significant weight loss at 6 and 12 weeks from baseline. The percentage of weight change from baseline was −4.02% (95% CI, −4.40 to −3.64) in IF 16:8, −3.15% (95% CI, −3.41 to −2.89) in IF 14:10, and −0.55% (95% CI, −1.05 to −0.05) in the control group at 12 weeks. The percentage of weight loss was significantly more in both IF groups than in the control group and was significantly more in IF 16:8 than IF 14:10 at 6 and 12 weeks (Figure 3a). The mean BW change from baseline was −3.18 kg (95% CI, −3.41 to −2.96 kg) in IF 16:8, −2.5 kg (95% CI, −2.65 to −2.35 kg) in IF 14:10 and −0.4 kg (95% CI, −0.78 to −0.03 kg) in the control group. The percent achieving weight loss ≥5% was highest in IF 16:8. However, only 15.2% of the participants in IF 16:8 had achieved 5% weight loss (Figure 3b).

Figure 3.

(a) Percent change of BW from baseline, (b) Percent BW loss.

FBS and HbA1C change from baseline

The mean change in FBS from baseline was −30.91 mg/dL (95% CI, −39.90 to −21.91 mg/dL) in IF 16:8, −28.06 mg/dL (95% CI, −38.83 to −17.29 mg/dL) in IF 14:10, −9.09 mg/dL (95% CI, −16.44 to −1.74 mg/dL) in the control group (Figure 4a). The mean HbA1C change from baseline was −0.499% (95% CI, −0.649 to −0.350%) in IF 16:8, −0.528% (95% CI, −0.715 to −0.340%) in IF 14:10, −0.197% (95% CI, −0.371 to −0.023%) in the control group (Figure 4b). The means of FBS and HbA1C were significantly decreased from baseline in all three groups. However, FBS and HbA1c were significantly decreased more in both IF groups than the control group, without a significant difference between the two IF groups.

Figure 4.

(a) Change in FBS from baseline, (b) Change in HbA1C from baseline.

Lipid change from baseline

The mean triglyceride (TG) was significantly decreased from baseline in all three groups. However, triglyceride significantly decreased more in the IF groups than in the control group, with no significant difference between the two IF groups (P = 0.490; Figure 5a). The total cholesterol and LDL decreased significantly from baseline in only in the two IF groups and decreased more in the two IF groups than the control group, with no significant difference between the two IF groups (Figure 5b,c). The mean HDL was significantly increased from baseline in all three groups and increased more in the two IF groups than in the control group, with no significant difference between the two IF groups (P = 0.434; Figure 5d).

Figure 5.

(a) Change in triglyceride from baseline, (b) Change in total cholesterol from baseline, (c) Change in LDL from baseline, (d) Change in HDL from baseline.

Hunger score and adverse effects

The mean hunger score in the two IF groups was significantly higher than the control group at 6 and 12 weeks. However, the hunger scores were only moderate (score 4–5 in the two IF groups and 2 in the control group), not too severe until the participants had to deviate from the protocol. There was no significant difference in the mean hunger score between the two IF groups (Table S1). The most common adverse effect was palpitations, followed by dizziness, abdominal pain, and mood change which were not significantly different between three groups. All three groups had no documented hypoglycemia and had no change in diabetic drug doses during the intervention (Table S2).

DISCUSSION

This study demonstrated that obese patients with type 2 diabetes mellitus who followed either IF16:8 or 14:10 consuming 3 days a week for 3 months duration had a significant loss of weight, a decrease in FBS and HbA1c, as well as an improvement in lipid profiles from baseline without a significant difference between the two intermittent fasting groups, except for weight loss which was significantly more in the IF 16:8 group, and significantly more than in the control group. Che et al., in a study in China, compared IF 14:10 (eating time from 8:00–18:00) every day with the control in type 2 diabetes mellitus obese patients for 12 weeks, and demonstrated that the mean change in BW from baseline was −2.98 kg in the 14:10 group, −0.83 kg in the control group (P < 0.001), FBS was −26 mg/dL from baseline in the 14:10 group, −14 mg/dL in the control group (P < 0.001), HbA1C was −1.54% in the 14:10 group and −0.66% in the control (P < 0.001) ¹² . The results were in the same trend as our study. The degree of weight loss was comparable to our study, however, the glycemic control was more in Che et al. study than in our study. The difference between the two studies was the frequency of IF 14:10 which was practiced every day in the Che et al. study but only 3 days/week in our study. The age of the participants had a wider range than our study (18–70 years) and a different nationality of the subjects. Yaun et al. did a systemic review and meta‐analysis of ten RCTs and supported that the IF helped to achieve BW loss and improvement in FBS by decreasing insulin resistance in obese patients ⁷ . Furthermore, the animal model showed that IF improved metabolism by acting through the molecular circadian clock and gut microbiome composition ⁹ .

The improvement in triglyceride with intermittent fasting in our study had the same results as the study of Hutchison et al. which assessed the effects of 9 h IF in prediabetic men in Australia ²⁰ . Gabel et al. found that intermittent fasting helped not only in decreasing in triglyceride and fat mass but also in decreasing oxidative stress ²¹ . The significant decrease in mean cholesterol and LDL from baseline in both IF groups in our study was the same result as a systematic review and meta‐analysis of Liu et al. which included 17 RCTs and showing that intermittent fasting had a beneficial effect in decreasing total cholesterol, and LDL, but no significant benefit in HDL ²² . Wilkinson et al. investigated the effect of a 10 h IF in patients with metabolic syndrome in the US and demonstrated that the LDL in the IF group decreased significantly when compared with baseline LDL (P = 0.016), but no significant change in HDL (P = 0.051) ²³ . Our study showed an improvement in HDL in the IF groups which was in contrast to the study of Cienfuegos et al. which compared 4 h IF (eating only from 3.00–7.00 pm) and 6 h IF (eating only from 1.00 to 7.00 pm) for 10 weeks in obese participants, who exercised less than 2 h/week and showed no significant increase in HDL level when compared with the control group and baseline HDL ²⁴ . The systematic review and meta‐analysis to compare the efficacy of intermittent fasting vs continuous energy restriction (CER) by Xu et al. showed intermittent fasting was more effective than CER in increasing HDL. Sundfør et al. showed IF in participants aged 21–70 years with obesity increased HDL. However, no data have explained the mechanism of HDL and IF until now ²⁵ , ²⁶ . In the animal model, IF without caloric restriction has been shown to prevent dyslipidemia and age‐related decline in cardiac function ⁹ . IF increased the expression of hepatic lipase and decreased the expression of the lipid droplet‐associated and lipolysis inhibitor gene ⁹ , ²⁷ . In addition, the results of improving in LDL and triglyceride level might decrease the cardiovascular risk in obese patients ²¹ .

In mouse studies, intermittent fasting during the dark cycle improved glucose tolerance, increased ghrelin, and reduced leptin ⁹ , ²⁸ , ²⁹ . However, in a human study, the ghrelin and leptin remained unchanged with early intermittent fasting, despite a subjective appetite improvement ⁹ , ³⁰ . In this study, subjects in both IF groups reported more hunger than subjects in the control group which is the same as the study of Sundfør et al. ²⁶ . A higher hunger score increases food craving ²⁶ and can increase the rate of non‐adherence to the protocol and causes weight to be regained particularly in the longer‐term study. Paoli et al. showed that eating breakfast, avoiding late‐night meals, and fasting from 12 to 16 h improved insulin sensitivity and decreased total cholesterol and hunger ³¹ . Therefore, intermittent fasting late‐night and eating during the day should improve metabolic parameters than fasting in the morning. Moro et al. reported that IF 16:8 for 8 weeks maintained muscle mass in 34 resistance‐trained males when compared with the normal diet group ³² , but our study did not record the data of muscle function. The strength of the study is that it is the first RCT to study varying hours of fasting time and fasting only 3 days a week for 3 months in IF groups and control group on weight loss and metabolic outcomes in obese diabetic Thais. The weakness of the study is that it was a single‐center study. The adherence to the fasting time was checked from the interview of food intake and 3 day food record only 3 days before each visit at 2, 6, and 12 weeks. The subjects might not eat in the same pattern every day. The limitation is the energy intake from 3 days food record might be not accurate or not represent all the intervention period.

In conclusion, both IF 16:8 and 14:10 when consumed 3 days a week for 3 months had benefits in losing weight and improving metabolic parameters in obese, type 2 diabetes mellitus Thais compared with the control group without any serious adverse effect or hypoglycemia. Intermittent fasting 16:8 had more benefit in losing body weight than IF 14:10.

FUNDING INFORMATION

This research was funded by the Endocrine Society of Thailand, the grant year 2021, and the article processing charge was funded by Chiang Mai University.

DISCLOSURE

There are no conflicts of interest to disclose.

Approval of the research protocol: This study was approved by the Research Ethics Committee on Human Rights Related to Research Involving Human Subjects, Chiang Mai University, Thailand (MED‐2564‐08471), date of approval: 23 November, 2021.

Informed consent: All participants were informed consent before enrolling in the study.

Registry and the registration no. of the study/trial: The trial was registered on Thai Clinical Trials (TCTR 20230131002), date of approval: 31 January, 2023.

Animal studies: There was no animal studies involved.

Supporting information

Table S1. Hunger score at 6 and 12 weeks.

Table S2. Adverse effects at 12 weeks.