ABSTRACT
Background
The maternal metabolic milieu is challenged during pregnancy and may result in unwarranted metabolic complications. A time-restricted eating (TRE) pattern may optimize the metabolic response to pregnancy by improving glucose metabolism and reducing circulating glucose concentrations, as it does in nonpregnant individuals.
Objectives
The objectives of this study were to 1) assess eating timing in pregnant women; 2) understand the perceptions of adopting a TRE pattern; 3) determine the barriers and support mechanisms for incorporating a TRE pattern; and 4) identify those most willing to adopt a TRE pattern during pregnancy.
Methods
This was a cross-sectional quantitative and quasi-qualitative online survey study for women who were pregnant at the time of study completion or had given birth in the prior 2 years. Group analyses were performed based off willingness to try a TRE pattern using chi-squared analyses, independent samples t-tests, or an analysis of variance. Three separate reviewers reviewed qualitative responses.
Results
A total of 431 women (BMI, 27.5 ± 0.3 kg/m2) completed the study. Of the participating women, 23.7% reported willingness to try a TRE pattern during pregnancy. Top barriers to adopting a TRE pattern during pregnancy were concerns for 1) safety; 2) nausea; and 3) hunger. The highest ranked support mechanisms were: 1) the ability to choose the eating window; 2) more frequent prenatal visits to ensure the health of the baby; and 3) receiving feedback from a dietician/nutritionist. Women who did not identify as White/Caucasian expressed a higher willingness to try a TRE pattern during pregnancy (P = 0.01). Women who were nulliparous expressed a higher willingness to try a TRE pattern (P = 0.05).
Discussion
TRE, an alternative dietary strategy shown to optimize metabolic control, may be effective to prevent and manage pregnancy-related metabolic impairments. To create an effective TRE intervention during pregnancy, the input of pregnant mothers is necessary to increase adherence and acceptability.
Keywords: intermittent fasting, gestational diabetes, gestational weight gain, eating patterns, obesity, circadian rhythm
Introduction
The maternal metabolic milieu is challenged during pregnancy to meet the needs of the developing fetus. Progressive increases in insulin resistance and lipid availability are adaptive traits to deliver growth-promoting nutrients through the placenta. These pregnancy-related metabolic perturbations are exacerbated by preexisting metabolic derangements, such as maternal obesity, and increase the risk of metabolic dysfunction, such as gestational diabetes mellitus (GDM) (1–3).
Elevated growth substrates (e.g., lipids and glucose) during pregnancy increase the risks for various adverse maternal outcomes, including preeclampsia, cesarean section, preterm delivery, and the development of cardiometabolic disease later in life. Hyperglycemia and hyperlipidemia are also associated with fetal risks, including macrosomia, neonatal hypoglycemia, shoulder dystocia, and increased neonatal intensive care unit admissions (4–6). Excess fetal exposure to glucose and lipids results in abnormal metabolic programming, including heightened glucose and adipose tissue accretion (7, 8).
Strategies for optimizing the maternal milieu across pregnancy commonly focus on limiting gestational weight gain (GWG). Lifestyle interventions beginning in early pregnancy that achieved improvements to the maternal diet and/or physical activity, as well as moderate reductions in weight gain, have largely failed to reduce incidences of cardiometabolic impairment and its downstream sequelae, including macrosomia, birth weight, or neonatal hypoglycemia (9, 10). There is a growing body of evidence to suggest that pregnancy weight gain, while the obvious product of diet (energy intake) and physical activity (and energy expenditure), is not the chief determinant of substrate availability across pregnancy (11, 12). Thus, novel interventions to attenuate circulating glucose and lipids during pregnancy are urgently needed.
One potential dietary therapeutic to alter substrate availability and the circulating metabolic milieu is time-restricted eating (TRE; i.e., limiting eating to only certain hours of the day) (13). The intent of a TRE pattern is to align eating events with circadian rhythms to optimize the metabolism and prolong the length of fasting between day-to-day food intakes. It was previously difficult to discern whether metabolic benefits from a TRE pattern were from a reduction in the eating window or in caloric intake (14). However, in nonpregnant populations, a eucaloric TRE pattern was shown to improve metabolic regulation, including enhanced metabolic flexibility and an improved 24-hour fat oxidation (15). In prediabetic men, TRE limited to 6 hours and starting between 06:30 and 08:30 improved insulin sensitivity, beta cell function, blood pressure, and oxidative stress within 5 weeks, independent of weight loss (16). Therefore, TRE during pregnancy may help to prevent prolonged elevations in glucose and lipids, glucose intolerance, and GDM and its associated adverse downstream outcomes, without the need to reduce caloric intake.
In pregnancy, a TRE pattern has been proposed as an advantageous strategy for the prevention and management of GDM (17–19). There are no randomized controlled trials testing the effects of a TRE pattern on pregnancy and offspring outcomes, yet observational studies revealed that a shortened eating window and prolonged overnight fasting were associated with reduced fasting glucose (20). A case study of TRE in 1 woman with a complicated case of GDM showed improved fasting glucose without adverse effects (19).
The acceptability of administering an intermittent fasting intervention during pregnancy is unknown, particularly in women at elevated risk of pregnancy-related metabolic complications (e.g., women with obesity). Therefore, the aims of this research study were to 1) assess eating timing in pregnant women; 2) understand the perceptions of adopting various intermittent fasting eating patterns during pregnancy; 3) determine the barriers and support mechanisms for incorporating such an eating pattern during pregnancy; and 4) identify the subgroups of women most willing to adopt a TRE pattern during pregnancy, with particular interest in women with obesity.
Methods
Study design
This was a cross-sectional quantitative and quasi-qualitative survey study. Women who were pregnant or had given birth in the prior 2 years were targeted to complete an online questionnaire specifically developed for this study. The questionnaire was tested for functionality and usability. Iterative feedback on survey content was provided from the initial concept to the final design from researchers with content (nutrition science) and methodological expertise, as well as from pregnant women and mothers. Questions were rephrased for clarity and adjustments were made based on aesthetics and to be optimized across various device formats (i.e., computers, tablets, and cellular devices). The survey was hosted on REDCap (Research Electronic Data Capture) (21) at Pennington Biomedical Research Center and was accessible for 4 months (December 2020 through March 2021). All collected data were deidentified.
Participants and recruitment
This study was approved by the Institutional Review Board at Pennington Biomedical Research Center. Participants were eligible to participate if they were female, 18 years of age or older, resided in the United States, and had access to the internet. Participants were recruited to the study from paid advertisements on various social media platforms. Recruitment ads were intended to reach a broad group of women and included diverse photographs of pregnant women and new mothers (e.g., various races and body sizes). The study was also advertised on the research center webpage and distributed via an email listserv and word of mouth. Upon entering the survey link, interested individuals received instructions that detailed the purpose of the research; after verifying eligibility criteria, individuals provided consent to participate. Participation in the survey was voluntary and upon completion of the survey, participants could elect to be eligible to receive 1 of 10 gift cards worth $50.
Survey design
The purpose of the survey was to assess eating patterns during pregnancy and assess perceptions of various eating patterns and exercise habits during pregnancy. The survey consisted of 40 items across 4 domains: 1) demographics, anthropometrics, and household information; 2) eating and exercise patterns during pregnancy; 3) perception of eating patterns during pregnancy; and 4) perceptions of exercise interventions during pregnancy. All data were self-reported. The survey was designed to be completed in approximately 15 minutes. Constructs utilized within the study were developed based off previously reported priorities for research participation from pregnant patients and interactions with research participants from previous TRE trials conducted in nonpregnant individuals (22). The last item of the survey allowed participants to provide free text on any additional information regarding their thoughts on fasting and/or eating behaviors during pregnancy. The survey instrument is provided as Supplemental Methods.
Willingness to follow an intermittent fasting eating pattern
Women were asked to report their willingness to follow 3 types of intermittent fasting patterns: 1) a TRE pattern; 2) alternate-day fasting; and 3) a 5:2 eating pattern. Each of the diets were accompanied by a simple definition. The respective definitions provided to women were as follows: 1) “restricting eating to only a certain number of hours per day (also called Time-Restricted Eating)”; 2) “eating every other day (also called the Alternate Day Fasting diet)”; and 3) “eating normally on 5 days per week and restricting eating on 2 days per week (also called the 5:2 diet).”
Responses for a TRE pattern were classified into a dichotomous response; “willing” and “not willing” to try TRE during pregnancy, using the following criteria:
| Classification | Description |
| “Willing” | “I have tried TRE during pregnancy and liked it” |
| “I have NOT tried TRE during pregnancy but would be willing to try it” | |
| “NOT willing” | “I have tried TRE during pregnancy and did not like it” |
| “I have NOT tried TRE during pregnancy and would NOT be willing to try it” |
Concerns and support mechanisms
Women were provided 8 concerns regarding following a TRE pattern during pregnancy. The following 8 concerns were provided as options: 1) “I would be too hungry”; 2) “I would get too nauseous”; 3) “I would not eat enough food”; 4) “it would be hard to eat a balanced diet”; 5) “it would not be safe for my health”; 6) “it would not be safe for my baby's health”; 7) “it would not work with my busy schedule”; and 8) “it would be hard to follow if my family doesn't join me.” Women were asked to report whether they were “very concerned,” “somewhat concerned,” “not very concerned,” or “not at all concerned” or could answer “I don't know” to each of the 8 concerns. Those concerns with the most “very concerned” responses were ranked as top concerns and items with the most “not at all concerned” responses were ranked as the lowest concerns.
Similarly, women were also provided 8 support mechanisms as options: 1) “being able to choose my own eating time window”; 2) “following the TRE plan for 5 days out of the week only”; 3) "being able to begin eating in the morning and stopping around 5 pm so that I would fast overnight”; 4) “being able to video chat with my dietician/nutritionist while I eat my dinner, since it will be outside the range of time that my family eats dinner”; 5) “being able to begin eating at lunch so I could stop eating around 8 pm (this means fasting less at night but fasting until lunch, or around 12 pm)”; 6) “using an app to log my eating times”; 7) “getting feedback from my dietician/nutritionist on my app logs so I can make sure what I am eating is healthy”; and 8) “checking in with my doctor more often to make sure my baby is healthy.” Women were asked to report these 8 support techniques as “not at all helpful,” “not very helpful,” “somewhat helpful,” or “very helpful” or could answer “I don't know.” Ranking of support mechanisms was analyzed by combining “not at all helpful” and “not very helpful” as “not helpful” and combining “somewhat helpful” and “very helpful” as “helpful.”
Statistical analysis
Participants who completed responses to all questions are included in the present analysis. Descriptive statistics (mean, frequencies, and percentages of the sample) were calculated to describe our sample. Outcome data are presented as either the mean ± SE or frequency (%). Group analyses were performed based on the willingness to try a TRE pattern during pregnancy. Subgroups of interest included BMI, parity, age, race, and marital status. BMI was calculated from self-reported height and weight. Women who reported being currently pregnant at the time of survey were asked their prepregnancy weight, and the prepregnancy weight was used to calculate BMI. Women who self-reported having underweight (calculated BMI <18.5; n = 6) were excluded from BMI subgroup analyses. Other subgroups of interest were existing eating patterns during pregnancy (time of eating) and health behaviors during pregnancy (perceived change toward more healthful eating and cardiovascular exercise). Chi-square analyses were performed to compare differences in frequency distribution between willingness groups. Continuous variables were assessed using independent-samples t-tests or an analysis of variance. All analyses were set with an alpha <0.05 as the predetermined level of significance. Responses to the last item of the survey (free-text box) were reviewed by 3 separate reviewers (EWF, MK, and JRS). Responses were coded by eye, and common themes that emerged from the responses were agreed upon between the 3 reviewers. Exemplar quotes pertaining to intermittent fasting and altered diet patterns during pregnancy are highlighted in the manuscript.
Results
Participants
A total of 641 women consented to participate in this study and initiated the questionnaire, and 431 completed the questionnaire in full and were included in the analysis. Of these, 88 (20.4%) were pregnant and had given birth in the prior 2 years, 199 (46.2%) were pregnant and had not given birth in the prior 2 years, and 144 (33.4%) were not pregnant and gave birth in the prior 2 years. The majority of participants were over 30 years of age, identified as White, and were multiparous. The mean BMI in the total sample was 27.5 ± 0.33 kg/m2, and more women reported having normal weight (40.1%), compared to overweight (28.3%) and obesity (29.7%). Participant characteristics are presented in Table 1.
TABLE 1.
Characteristics of women willing and not willing to try time restricted eating during pregnancy
| All, N = 431 | Would be willing, n = 102 | Would not be willing, n = 329 | Between-group differences (P value) | |
|---|---|---|---|---|
| Characteristics | ||||
| Age category, years | — | — | — | 0.941 |
| ≤30 years, n (%) | 193 (44.8) | 46 (45.1) | 147 (44.7) | |
| >30 years, n (%) | 238 (55.2) | 56 (54.9) | 182 (55.3) | |
| Race | — | — | — | 0.011,2 |
| White/Caucasian, n (%) | 364 (84.5) | 78 (76.5) | 286 (86.9) | |
| Other, n (%) | 67 (15.5) | 24 (23.5) | 43 (13.1) | |
| Pre-pregnancy BMI category,3 kg/m2 | — | — | — | 0.191 |
| Underweight, n (%) | 6 (1.4) | 0 (0) | 6 (1.8) | |
| Normal weight, n (%) | 175 (40.1) | 35 (34.3) | 140 (42.6) | |
| Overweight, n (%) | 122 (28.3) | 31 (30.4) | 91 (27.7) | |
| Obesity, n (%) | 128 (29.7) | 36 (35.3) | 92 (28) | |
| Marital status | — | — | — | 0.611 |
| Married, n (%) | 366 (84.9) | 85 (83.3) | 281 (85.4) | |
| Not married, n (%) | 65 (15.1) | 17 (16.7) | 48 (14.6) | |
| Pre-pregnancy weight, kg | 74.8 ± 0.9 | 77.3 ± 1.8 | 74.1 ± 1.1 | 0.154 |
| Pre-pregnancy BMI, kg/m2 | 27.5 ± 0.3 | 28.5 ± 0.6 | 27.2 ± 0.4 | 0.104 |
| Parity | — | — | — | 0.051 |
| Multiparous, n (%) | 323 (74.9) | 69 (67.6) | 254 (77.2) | |
| Nulliparous, n (%) | 108 (25.1) | 33 (32.4) | 75 (22.8) | |
| Behaviors | ||||
| Timing of first meal | — | — | — | 0.0011,2 |
| Within 30 minutes, n (%) | 237 (55) | 41 (40.2) | 196 (59.6) | |
| After 1 hour, n (%) | 194 (45) | 61 (59.8) | 133 (40.4) | |
| Eat healthier during pregnancy | — | — | — | 0.191 |
| Yes, n (%) | 221 (51.3) | 48 (47.1) | 173 (52.6) | |
| No, n (%) | 210 (48.7) | 54 (52.9) | 156 (47.4) | |
| Eat more food during pregnancy | — | — | — | <0.0011,2 |
| Yes, n (%) | 262 (60.8) | 44 (43.1) | 218 (66.3) | |
| No, n (%) | 169 (39.2) | 58 (56.9) | 111 (33.7) | |
| Performed cardio exercise during pregnancy | — | — | — | 0.851 |
| Yes, n (%) | 299 (69.4) | 70 (68.6) | 229 (69.6) | |
| No, n (%) | 132 (30.6) | 32 (31.4) | 100 (30.4) | |
Data are presented as N (%) or Mean ± Standard error of the mean.
1Statistical testing performed using Chi-squared analyses.
2denotes significance (P < 0.05).
3BMI classifications: underweight (<18.5 kg/m2), normal weight (18.5–24.9 kg/m2), overweight (25–29.9 kg/m2), obesity (≥30 kg/m2).
4Statistical testing performed using independent samples t-test.
Eating patterns and hunger during pregnancy
The majority of women reported eating 3 meals (74.5%) and 2 or 3 snacks per day (36.7% and 34.3%, respectively) during pregnancy. Meals were defined as “food eaten that contains the calories and nutrients you need to keep you full, such as breakfast, lunch, and dinner,” and snacks were defined as “foods or drinks (other than water) that you eat or drink between meals.” Almost all women reported hunger upon waking in the morning (74.2%). The first meal or snack for the day was commonly consumed within 30 minutes of waking (55.0%) and most reported consuming their first meal within the first hour of waking (75.4%). However, approximately half of women reported that they typically eat or drink a caloric beverage prior to their first meal or snack of the day (e.g., coffee with cream or sugar, juice, or soda; 41.8%). The last meal of the day was commonly consumed at least 3 hours before bed (44.4%), but many women reported consuming an additional snack or caloric beverage between the last meal and when they went to sleep (66.2%). Of these women, 33.6% reported eating this snack within 30 minutes of going to bed. Furthermore, several women reported waking up hungry in the middle of the night (29.2%) and some women reported eating calorie-containing items during midnight awakenings (17.2%).
The number of meals or snacks eaten or the timing of the first meal or snack after awakening did not differ within parity or age. Yet, there was a significant difference among different BMI groups and the timing of the first meal or snack of the day [X2(2) = 30.759; P < 0.001]. Individuals having normal weight (86%) and overweight (77%) reported a higher incidence of eating within the first 60 minutes of waking compared to women with obesity (59%).
Attitudes toward TRE during pregnancy
The majority of women had not tried a TRE pattern while pregnant (93.5%). While half of women agreed that a TRE pattern is safe during pregnancy (47.3%), approximately one-fourth of women would be willing to try a TRE pattern during pregnancy to improve their health (23.7%).
Of the 8 concerns women were asked to consider in relation to following a TRE eating pattern during pregnancy, the top 3 concerns in rank order were: 1) the eating pattern would not be safe for the baby's health (50.6%); 2) nausea (50.3%); and 3) hunger (42.7%). The lowest ranked concerns were the following (in order): 1) difficulties eating a balanced diet (17.4%); 2) difficulties due to a busy work schedule (26.2%); and 3) difficulties adhering if the whole family did not also follow the same pattern (27.4%). The highest and lowest ranked concerns did not differ when looking only at those willing to TRE during pregnancy.
Regarding the usefulness of mechanisms to support pregnant women adhering to a TRE pattern, having the ability to choose the eating window was ranked as the highest strategy (88.0%). Interestingly, the preference to eat in the morning (fast throughout the evening) compared to start eating in the afternoon (fast in the late morning) was approximately equal (start eating in morning, 53.1%; start eating in afternoon, 46.9%). Women having obesity had the highest preference to start eating in the afternoon after fasting overnight and through the morning (58.6%), compared to women having normal weight (40.0%) or overweight [45.1%; X2(2) = 10.53; P = 0.005]. The second highest ranked strategy was for more frequent check-ups with a prenatal provider to ensure the baby was healthy (87.8%). The ability to receive nutrition feedback from a dietician or using a mobile app was the third highest helpful strategy (83.7%). Similar to the concern rankings, the 3 highest ranked support mechanisms did not differ between the whole sample and those willing to try a TRE pattern during pregnancy.
Women were asked to indicate the length of time they would be willing to fast. The following example was provided as part of the question: “for example, if you ate your dinner at 7:00 PM and did not eat again until 9:00 AM, this would be a 14-hour fast.” Women could respond with “less than 5 hours,” in 1-hour increments between 6 and 18 hours, or with “more than 18 hours.” The desired fasting duration of respondents is shown in Figure 1. As shown, the most commonly reported length of perceived fast duration was 12 hours (23.9%), and 23.4% of women reported that they could fast for more than 14 hours. There was no difference in the length of perceived fast between those who indicated a preference to fast in the morning compared with the evening (average length of time for morning fast: 10.7 ± 0.3 hours; average length of time for evening fast: 10.2 ± 0.22 hours; P = 0.19; “less than 5 hours” and “more than 18 hours” were computed as 5 and 19 hours, respectively). There were no differences in the desired length of fast among individuals >30 and ≤30 years of age (P = 0.15) or based on parity (P = 0.08) or BMI (P = 0.71). A subgroup analysis showed that women who reported a willingness to try TRE during pregnancy reported a slightly longer fast of 11.9 ± 0.4 hours.
FIGURE 1.
Length of time willing to fast during pregnancy for the total sample (n = 431), for women who indicated a preference to fast in the morning (i.e., initiate eating in the afternoon; n = 202), and for women who indicated a preference to fast in the evening (i.e., initiate eating in the morning; n = 229).
Attitudes toward alternative fasting approaches
Given that our study objective was to identify willingness to try eating patterns that incorporated fasting routines, we asked participants about their feelings towards a variety of fasting approaches. When asked about following a 5:2 diet, approximately one-fourth of women reported interest in trying this eating pattern during pregnancy (24.1%). Alternatively, when asked about following an alternate-day fasting pattern, very few women reported being willing to try this pattern during pregnancy (6.5%).
Characteristics and behaviors of those willing to try TRE during pregnancy
Upon exploring subgroups in willingness (willing/not willing) to try a TRE pattern during pregnancy, we found no differences in age (P = 0.94), BMI (P = 0.19), or marital status (P = 0.61; Table 1). There was a significant difference between pregnancy status and willingness to try a TRE pattern during pregnancy. Individuals who were pregnant reported more willingness to try a TRE pattern during pregnancy compared to individuals who were no longer pregnant [X2(1) = 7.086; P = 0.008]. Women who did not self-identify as White/Caucasian reported a higher proportion of willingness to try a TRE pattern during pregnancy [White/Caucasian: 21.4% willing; other races/ethnicities: 35.8% willing; X2(1) = 6.488; P = 0.01]. Lastly, women who were nulliparous tended to be more willing to try a TRE pattern (30.6% willing) compared to women who were multiparous [21.4% willing; X2(1) = 3.787; P = 0.05].
To identify other health behaviors which may be associated with willingness to try a TRE pattern, we evaluated willingness by eating patterns and exercise habits during pregnancy. Women who reported eating later after awakening reported a greater willingness to try a TRE pattern [14.2% of those who reported eating after 1 hour of waking compared to 9.5% of those who reported eating within 30 minutes of waking; X2(1) = 11.81; P = 0.001]. To determine whether a conscious effort to eat healthier during pregnancy was associated with willingness to try a TRE pattern, we looked at self-reported changes in eating behaviors with pregnancy. In total, half (51.3%) of respondents reported eating healthier during their pregnancy and there was no difference between those who reported an increase in healthful eating and those whose did not report eating healthier in their willingness to try a TRE pattern during pregnancy (P = 0.19). Most women reported eating more food during their pregnancy (60.8%). Women who reported not eating more food during pregnancy (i.e., eating less or the same amount of food as pre-pregnancy) were more willing to try a TRE pattern (13.5%) compared to those reported eating more during pregnancy [10.2%; X2(1) = 17.67; P < 0.001]. In relation to exercise habits during pregnancy, most women reported doing some form of cardiovascular exercise (69.4%). We observed no differences in willingness to try a TRE pattern among those who reported cardiovascular exercise and those who did not [X2(1) = 0.035; P = 0.852].
Additional opinions towards fasting patterns during pregnancy
Women were provided the opportunity to express any additional concerns or thoughts on intermittent fasting that were not covered by the survey using a free-text box. In total, 70 women provided additional opinions towards diet patterns, food intake, and exercise during pregnancy. Overall, 5 overarching topics related to intermittent fasting were observed, including: 1) perceptions on willingness; 2) consulting with a health-care provider prior to starting a diet during pregnancy; 3) gestational diabetes diagnosis; 4) individualized pregnancy health risks; and 5) personal experiences of eating patterns during pregnancy. Selected exemplar quotes from survey respondents within the 5 observed themes are highlighted in Table 2. Safety concerns for prolonged fasting during pregnancy was another apparent topic with conflicting viewpoints. One woman noted that she would be “really open to trying these [eating patterns]!,” while other women feared the health and safety of their pregnancy. For some women, willingness to engage in a TRE pattern during pregnancy was contingent on seeking help from a prenatal care provider. Yet, mixed positive and negative reactions were observed among those consulting with a prenatal care provider for eating pattern prescriptions during pregnancy. For example, 1 individual noted that women should “talk with their physician” before embarking on a prenatal diet, while another opposed with “I wouldn't trust any doctor who recommended a diet during pregnancy.” Four women expressed concerns over altering eating patterns and specified that these stemmed from their diagnosis of GDM. While some concerns for incorporating fasting patterns in those with a GDM diagnosis were vague, 1 woman was concerned that GDM would raise blood sugar. Few women acknowledged that pregnancy coupled with preexisting health concerns, such as hypertension, could influence the urgency for implementation of a TRE or alternate eating pattern, while others did not. Lastly, anecdotal evidence of a TRE pattern was provided from women who voluntarily restricted their eating window during pregnancy. In all, these collective viewpoints provide valuable insight of real thoughts and perceptions of a TRE pattern during pregnancy from pregnant or recently pregnant women.
TABLE 2.
Quotes from survey respondents on trying a time-restricted eating pattern during pregnancy
| Topic | Positive reactions | Negative reactions |
|---|---|---|
| Perceptions on willingness | “I am really open to trying these! And planning to get pregnant again soon!” | “No one should fast for 16 hours during any phase of pregnancy.” |
| “From 24 weeks to right now 28 weeks, I have started skipping breakfast and love it. … I look forward to continuing my vegetarian diet and this fasting through the end of my pregnancy.” | — | |
| Consulting with health-care provider | “I don't think women should consider dieting unless they talk with their physician first.” | “I wouldn't trust any doctor who recommended a diet during pregnancy.” |
| “I do not know enough about these diet programs to know if they are safe during pregnancy. I assume that they are but I would personally want to consult with my doctor and a nutritionist if I were going to go on a special diet during pregnancy.” | — | |
| Gestational diabetes diagnosis | — | “Intermittent fasting is not safe for pregnancy. No pregnant mom should do that diet, especially if they have nutrition concerns like gestational diabetes.” |
| — | “I had gestational diabetes during my pregnancy so I would be concerned because fasting can raise sugar levels.” | |
| Individualized pregnancy health risk | “In my opinion, I do not think pregnant women should be dieting at all unless you are already obese when you become pregnant.” | “I don't really believe sticking to a specific diet plan is realistic during or outside of pregnancy regardless of health benefits or risks.” |
| “Intermittent fasting seems extreme.… That said, I haven't had issues with weight gain or blood pressure during either of my pregnancies so maybe I'm coming from a different place.” | “I guess I'm trying to understand the need for pregnant women to fast? I have a low BMI and never gain more than the recommended amount of weight while pregnant.” | |
| “I have restricted my eating window not for fasting purposes, but because I get terrible acid reflux at night if I eat too close to bedtime.” | “I need to eat frequently during pregnancy or I get very nauseous. I wouldn't ever consider following any sort of intermittent fasting or reduced calorie windows.” | |
| Personal experience | “I have been doing intermittent fasting for the past 2 years. When I got pregnant, I didn't find out until I was 9 weeks along and did continue my fasting.” | — |
Discussion
Elevated maternal metabolic substrates during pregnancy increase the risk for the development of metabolic disturbances, thereby increasing risks for adverse pregnancy and offspring outcomes. The objective of this study was to gain insight to eating patterns during pregnancy and to gauge attitudes towards adopting an intermittent fasting eating pattern; specifically, a TRE pattern to improve maternal and offspring health. In the present study of 431 women either currently pregnant or pregnant within the prior 2 years, it was apparent that many barriers and concerns exist for the adoption of TRE during pregnancy. While only 23.7% of women would be willing to try TRE during the second and third trimester of pregnancy to improve their health, the study exposed many ways in which pregnant women could be supported during a TRE approach to improve the acceptability of an intervention. In addition to perceived barriers, key mechanisms of support were identified. To our knowledge, this is the first study to examine thoughts and perceptions of implementing a TRE pattern during pregnancy for the purpose of health promotion.
The first-line prevention and treatment of impaired metabolism during pregnancy is lifestyle modifications, including dietary changes, increased physical activity, and self-monitoring of blood glucose (23). However, it has been shown that prescribed lifestyle changes are not effective in improving the maternal metabolic milieu and downstream offspring outcomes, even in the presence of reduced GWG (9, 10). Adherence to dietary interventions are often low and may result in counterproductive dietary changes, such as increased fat intake (24), which poses an additional risk for fetal development (25). A recent study testing a diet with a modest reduction to carbohydrate intake during pregnancy found no differences in infant outcomes, including birth size or adiposity (24). Therefore, it is time to challenge existing strategies and develop alternative dietary interventions that alter the maternal metabolic milieu. There has been a call to action to identify innovative approaches that are more effective in changing nutrition behaviors (26). A TRE pattern may fill this gap as an innovative dietary therapeutic to alter the metabolic status. Alarmingly, women with obesity are less likely to make necessary dietary changes in response to a diagnosis of metabolic impairment, such as GDM (26), placing them at an elevated risk of future adverse events. Furthermore, women with obesity report greater nighttime carbohydrate consumption, which is associated with worsened glucose homeostasis (27). In the present study, women of varying pre-pregnancy BMI classes all expressed similar willingness to engage in a TRE pattern during pregnancy if it were shown to be beneficial for their health and the health of their baby. As such, TRE may be a more desirable eating pattern compared to traditional calorie or carbohydrate counting (28) for individuals most at need for intervention, since expectant mothers can eat ad libitum. A TRE pattern would allow a diet to be tailored towards individual food preferences within certain eating windows.
Outside of pregnancy, a TRE pattern has been shown to have beneficial effects on the metabolic milieu, independent of weight loss. There is evidence to support the link between the eating window and glucose regulation. For example, an acute study of a TRE pattern over 4 days with an eating window of 6 hours each day was shown to improve metabolic flexibility and reduce the 24-hour respiratory quotient (i.e., increased fat oxidation) (15). Studies longer in duration showed that limiting eating to only 8 hours of the day and beginning eating in the morning has been identified as a strategy to improve insulin sensitivity, beta cell responsiveness, and fasting concentrations of glucose and insulin (16, 29). Given these robust effects, it is logical to tailor such an intervention for pregnant women at risk of developing glucose intolerance. Certainly, pregnant women have unique needs. In our study, we found that almost half of participants reported hunger as a significant concern for TRE during pregnancy. This is important to note as conversely, in aforementioned trials, a TRE pattern has been shown to reduce appetite and hunger levels and improve sense of fullness (15, 16).
Although a 16-hour fast may not be feasible for all pregnant women, an extension of the woman's current fasting window may provide a valuable starting point. A recent study at midpregnancy observed that each 1-hour increase to overnight fasting was associated with a 0.03 mmol/L decrease in fasting glucose concentrations (20). This indicates that even modest reductions to the eating window may be beneficial to establish a healthy pregnancy maternal metabolic milieu. While classic TRE studies have not been performed during pregnancy, religious fasting, such as Ramadan, provide a natural experiment of a TRE pattern during pregnancy (30). Ramadan is a Muslim holiday in which food and water are avoided from sunrise to sunset. While pregnant women are often exempt from participating in the holiday, many choose to partake. Pregnant women who partake in Ramadan during their second trimester have a significantly lower incidence of GDM (2.6% compared to 8.3% in nonfasting women) and their risk for developing GDM is 1.5 times lower (31). Outside of religious fasting, a TRE pattern during pregnancy has not been extensively studied. A case report of 1 woman with GDM revealed that fasting 13–15 hours per day maintained postprandial glucose concentrations within normal ranges, after traditional GDM diets failed to produce meaningful results (19). Together, these data provide compelling evidence in support of developing an innovative TRE intervention during pregnancy.
Before administering a novel intervention to a vulnerable population, there is a need to codevelop interventions with the desired recipient: in this case, the pregnant individual. In conventional research, inappropriate recommendations are often a result of failure to take into account relevant priorities and perspectives of the desired recipient (32). Development of a successful intervention with input from relevant parties (e.g., clinicians and pregnant individual) is a long yet valuable process that may evolve to include options and programs that may not have been previously considered by research teams. An ongoing randomized controlled trial for GDM treatment recently adopted an extensive intervention development and coproduction design including evidence reviews and stakeholder consultation, coproduction with the end user, and prototyping the intervention in a small sample with focus groups and interviews prior to finalizing it (33). Conducting a needs assessment is essential when designing interventions for special and vulnerable populations, such as pregnant women. Specifically, interventions during pregnancy require unique considerations for cravings, excessive hunger, and nausea, as well as for the comfort and safety of the mother and developing fetus. Results from the present study revealed obvious concerns over implementing a TRE pattern during pregnancy, which should be considered while designing such an intervention. Notably and unexpectedly, some women noted that their GDM diagnosis would be a barrier to partaking in a TRE pattern during pregnancy, in fear that this would elevate their blood glucose. This insight was provided through quasi-qualitative data and this concern was not originally conceived by the research team. This feedback enlightened us that special education, together with glucose monitoring, may assist pregnant women with diagnosed GDM. Of the 8 provided concerns, the most common significant concern was for the safety of the developing fetus. It is important that this concern be met with increased clinician contacts and frequency of fetal ultrasounds to monitor growth and development. Appropriately, women in the study ranked this support mechanism the highest. Other support mechanisms included meeting with nutritionists and dieticians to ensure adequate nutrition during an intervention and an optimal design to foster recommended weight gain. This provides the ideal opportunity for the use of telehealth and mobile technology, such as apps, for patients to log daily fasting and postprandial glucose levels, along with daily food and eating times, and receive appropriate counseling. Patients should be counseled to understand that a TRE pattern may promote improvements to the maternal metabolic milieu without the need to change calorie intake. Given that traditional prenatal interventions fail to achieve desired maternal and offspring effects, there is an urgent need to codevelop novel interventions with buy-in from pregnant women.
This study is strengthened by the input of over 400 women. The sample is diverse in body weight status and includes women with both current and recent pregnancies. It is worth noting that there are inherent limitations of survey data, including the attainment of self-reported data. To eliminate missing data, we elected not to incorporate open-ended questions during the survey design, except for the final free-text box regarding additional thoughts and considerations. This study design limited responses to a list of prespecified concerns, barriers, and facilitators, which were ranked by study participants. Even though the survey allowed for participants to provide additional concerns, barriers, and facilitators, they may have neglected to do so. Our recruited sample may also reflect selection bias. The recruitment of the study was mainly limited to those with access to the internet and who use social media. Additionally, we do not know the health status of these participants beyond BMI classification. It is possible that women who have experience with pregnancy-related metabolic diseases or a prior pregnancy with excess GWG would be more willing to try such an intervention. Another limitation is that we were unable to educate survey respondents on the specifics of following a TRE pattern. Prior to questions related to a TRE pattern, a brief TRE pattern description was provided as “researchers have shown that eating all your calories per day in a window of 6–8 hours and fasting (not eating) for 16–18 hours per day decreased appetite and had beneficial changes on health. Fasting excludes all foods and drinks except for water and non-caloric drinks.” Therefore, it is possible that women had misconceptions about TRE that were unable to be addressed, such as a mandatory reduced caloric intake or strict eating/fasting lengths.
In conclusion, considering the acute and long-term impacts of elevated substrates during pregnancy on mother and child, alternative therapeutics to optimize metabolic control of glucose and lipids throughout pregnancy are greatly needed. Pregnancy represents a unique time, with physiological and emotional considerations. Thus, there is a necessity for precision prevention and treatment of pregnancy-related metabolic disturbances to curb the intergenerational transmission of obesity and metabolic disease. The potential benefits of a TRE pattern during pregnancy may prove to be a powerful management tool. To create the most effective intervention, it is important to codevelop these plans with mothers and stakeholders in order to increase adherence and acceptability and to design trials to evaluate efficacy.
Supplementary Material
ACKNOWLEDGEMENTS
The author responsibilities were as follows—EWF: analyzed the data, performed statistical analyses, and drafted the manuscript; MK, JRS, and LMR: contributed to critical revision of the manuscript; and all authors: designed and conducted the research, had primary responsibility for the final manuscript, and read and approved the final manuscript.
Notes
Funding: National Institutes of Health (NIH) grants R01 NR017644, R01 DK124806, P30 DK072476.
Author disclosures: The authors report no conflicts of interest.
Supplemental Methods are available from the “Supplementary data” link in the online posting of the article and from the same link in the online table of contents at https://academic.oup.com/jn.
Abbreviations used: GDM, gestational diabetes mellitus; GWG, gestational weight gain; TRE, time-restricted eating.
Contributor Information
Emily W Flanagan, Pennington Biomedical Research Center, Baton Rouge, LA, USA.
Maryam Kebbe, Pennington Biomedical Research Center, Baton Rouge, LA, USA.
Joshua R Sparks, Pennington Biomedical Research Center, Baton Rouge, LA, USA.
Leanne M Redman, Pennington Biomedical Research Center, Baton Rouge, LA, USA.
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