Effect of intermittent fasting on circulating inflammatory markers in obesity: A review of human trials

Obesity is associated with low-grade inflammation. Weight loss, by means of dietary restriction, has been shown to reduce systemic inflammation. Intermittent fasting has recently gained popularity as a weight loss diet, but its effects on inflammatory markers in individuals with obesity have yet to be summarized. Accordingly, this review examined how the two main forms of intermittent fasting, i.e., time restricted eating (TRE) and alternate day fasting (ADF), impact body weight and key circulating inflammatory markers (i.e., C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-alpha), and interleukin-6 (IL-6)), in adults with obesity. Results from this review reveal that TRE with various eating window durations (4–10 h per day) has no effect on circulating levels of CRP, TNF-alpha or IL-6, with 1–5% weight loss. As for ADF, reductions in CRP concentrations were noted when >6% weight loss was achieved. However, ADF had no effect on TNF-alpha or IL-6 concentrations, with this degree of weight loss. Thus, intermittent fasting has little or no effect on key inflammatory markers, but more research is warranted to confirm these preliminary findings

Time Restricted Feeding (4-hour versus 6-hour) for Weight Loss in Obese Adults

Time restricted feeding (TRF) is a form of intermittent fasting that has gained substantial popularity over recent years as a weight loss regimen. Despite its growing popularity, very few studies have examined the weight loss efficacy of this diet. TRF involves eating within a specific window of time each day, and water fasting for the rest of the day. The goal of this study was to compare the effects of a 4-h TRF versus 6-h TRF on body weight, metabolic disease risk factors, inflammation, and sleep, in adults with obesity. Subjects with obesity (n = 58) were randomized to 1 of 3 groups: 1) 4-h TRF (ad libitum feeding between 3pm to 7pm, water fasting between 7pm to 3pm), 2) 6-TRF (ad libitum feeding between 1pm to 7pm, water fasting between 7pm to 1pm), or 3) control group (usual diet with no meal timing restrictions) for 8 weeks. Results from this study show that 8 weeks of 4-h and 6-h TRF decreases body weight by -3.2% and -3.2%, respectively, relative to controls. Subjects were adherent to the prescribed eating window on 6.2 days per week, and this level of adherence remained constant throughout the 8-week trial. Our findings also indicate that reducing the daily eating window to either 4-h or a 6-h decreases caloric intake by ~550 kcal/d, without intentional calorie counting. Both TRF interventions produced significant reductions in fasting insulin, HOMA-IR (measurement of insulin resistance) and oxidative stress, versus controls. However, other metabolic disease risk parameters such as plasma lipids, blood pressure, and inflammation, remained unchanged. As for sleep, sleep quality and duration remained unchanged in all groups. Our results also suggest that TRF is a safe diet therapy that does not induce any significant adverse effects. These data offer promise for the use of shorter (4-h and 6-h) eating windows as safe and effective weight loss regimens in adults with obesity. However, longer-term, larger-scale randomized controlled trials will be required before solid conclusions can be reached

Alternate Day Fasting Combined with a Low Carbohydrate Diet: Effect on Sleep Quality, Duration, Insomnia Severity and Risk of Obstructive Sleep Apnea in Adults with Obesity

Background: Alternate day fasting combined with a low carbohydrate diet (ADF-LC) is an effective weight loss regimen. Whether the weight loss induced by ADF-LC can improve sleep, remains unknown. Objective: This study examined the effect an ADF-LC diet on sleep quality, duration, insomnia severity and the risk of obstructive sleep apnea. Methods: Adults with obesity (n = 31) participated in ADF (600 kcal “fast day”; ad libitum intake “feast day”) with a low-carbohydrate diet (30% carbohydrates, 35% protein, and 35% fat). The 6-month trial consisted of a 3-month weight loss period followed by a 3-month weight maintenance period. Results: Reductions in body weight (−5 ± 1 kg, p < 0.001) and fat mass (−4 ± 1 kg, p < 0.01) were noted during the weight loss period, and these reductions were sustained during the weight maintenance period. Lean mass and visceral fat remained unchanged. The Pittsburgh Sleep Quality Index (PSQI) score indicated poor sleep quality at baseline (6.4 ± 0.7) with no change by month 3 or 6, versus baseline. ISI score indicated subthreshold insomnia at baseline (8.5 ± 1.0), with no change by month 3 or 6, versus baseline. The percent of subjects with high risk of obstructive sleep apnea at baseline was 45%, with no change by month 3 or 6. Wake time, bedtime, and sleep duration remained unchanged. Conclusion: The ADF-LC diet does not impact sleep quality, duration, insomnia severity or the risk of obstructive sleep apnea in adults with obesity

Protocol for measuring intrahepatic triglyceride content in adults with non-alcohol fatty liver disease

Summary: Here, we present a protocol for conducting magnetic resonance imaging proton density fat fraction (MRI-PDFF) to measure intrahepatic triglyceride (IHTG) content in adults with non-alcohol fatty liver disease (NAFLD). We describe steps for screening patients for NAFLD, MRI-PDFF scanning, and using MRI-PDFF data to quantify IHTG. This protocol can be repeated sequentially and used in weight loss trials. However, it is limited to patients with NAFLD as it does not assess non-alcoholic steatohepatitis or hepatic fibrosis.For complete details on the use and execution of this protocol, please refer to Ezpeleta et al. (2023).1 : Publisher’s note: Undertaking any experimental protocol requires adherence to local institutional guidelines for laboratory safety and ethics

Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials

Intermittent fasting is a popular diet for weight loss, but concerns have been raised regarding the effects of fasting on the reproductive health of women and men. Accordingly, we conducted this literature review to clarify the effects of fasting on reproductive hormone levels in humans. Our results suggest that intermittent fasting decreases androgen markers (i.e., testosterone and the free androgen index (FAI)) while increasing sex hormone-binding globulin (SHBG) levels in premenopausal females with obesity. This effect was more likely to occur when food consumption was confined to earlier in the day (eating all food before 4 pm). In contrast, fasting did not have any effect on estrogen, gonadotropins, or prolactin levels in women. As for men, intermittent fasting reduced testosterone levels in lean, physically active, young males, but it did not affect SHBG concentrations. Interestingly, muscle mass and muscular strength were not negatively affected by these reductions in testosterone. In interpreting these findings, it is important to note that very few studies have been conducted on this topic. Thus, it is difficult to draw solid conclusions at present. From the limited data presented here, it is possible that intermittent fasting may decrease androgen markers in both genders. If this is the case, these results would have varied health implications. On the one hand, fasting may prove to be a valuable tool for treating hyperandrogenism in females with polycystic ovarian syndrome (PCOS) by improving menstruation and fertility. On the other hand, fasting may be shown to decrease androgens among males, which could negatively affect metabolic health and libido. More research is warranted to confirm these preliminary findings