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.

The aim of this secondary analysis was to compare the effects of time-restricted eating (TRE) versus calorie restriction (CR) and controls on sleep in adults with type 2 diabetes (T2D). Adults with T2D (n = 75) were randomized to 1 of 3 interventions for 6 months: 8 h TRE (eating only between 12 and 8 pm daily); CR (25% energy restriction daily); or control. Our results show that TRE has no effect on sleep quality, duration, insomnia severity, or risk of obstructive sleep apnea, relative to CR and controls, in patients with T2D over 6 months.

Background/Objectives: Obesity is associated with chronic systemic inflammation and elevated levels of inflammatory cytokines such as tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and C-reactive protein (CRP). Weight loss through lifestyle interventions can reduce inflammation in adults with obesity. Time-restricted eating (TRE) and calorie restriction (CR) are two popular diet interventions that can produce clinically significant weight loss. However, to date, no studies have directly compared the effects of TRE versus CR on inflammatory cytokines in adults with obesity. Methods: Here, we performed a secondary analysis on a recently published study to compare the long-term (12-month) effects of TRE versus CR on key inflammatory cytokines. Results: We found that while TRE and CR produced similar amounts of weight loss (4–5% from baseline), no statistically significant changes in circulating levels of TNF-alpha, IL-6, and CRP were noted in the TRE or CR groups, compared to the controls, by month 12. However, we did observe that circulating CRP levels were positively related to body weight, visceral fat mass, and insulin resistance, while IL-6 and TNF-alpha were not related to any metabolic marker. Conclusions: Thus, TRE and CR may not affect key inflammatory mediators with 4–5% weight loss, but more research is warranted.

Background/Objectives: This secondary analysis aimed to compare the effects of time-restricted eating (TRE) versus calorie restriction (CR) and controls on mood and quality of life in adults with type 2 diabetes (T2D). Methods: Adults with T2D (n = 69) were randomly assigned to one of three interventions for 6 months: 8 h TRE (eating only between 12 and 8 pm daily); CR (25% energy restriction daily); or a no-intervention control group. At baseline and 6 months, mood was assessed using the Beck Depression Inventory-II (BDI-II) and the Profile of Mood States (POMS) questionnaires, while quality of life was assessed using the Rand 36-Item Short Form (SF-36). Results: Body weight significantly decreased in the TRE group (−3.38%; 95% CI, −6.04 to −0.71%, p = 0.008), but not in the CR group (−1.80%, 95% CI, −4.50 to 0.91%, p = 0.32) versus controls by month 6. Fat mass, lean mass, and visceral fat mass remained unchanged in TRE and CR groups, versus controls, from baseline to month 6. No changes were observed in depression scores (BDI-II), total mood disturbance, or any POMS subscales (tension, depression, anger, fatigue, confusion, or vigor) in either the TRE or CR groups compared to controls. Similarly, there were no significant changes in the quality-of-life SF-36 constructs of vitality, bodily pain, mental health, and general physical health in the TRE or CR group versus controls. By month 6, there were no associations between changes in body weight, quality of life, and mood outcomes in any group. Conclusions: In conclusion, our findings suggest that TRE and CR do not have any effect on mood or quality of life in adults with T2D, relative to controls. However, the participants’ baseline mood and quality of life were generally within healthy ranges, and only minimal weight loss was achieved (3.5%, TRE only), which may explain the lack of observed effects.