Highlights d 4-and 6-h time-restricted feeding regimens were tested in adults with obesity d Both regimens produce similar weight loss over the 2 months of the study d Both regimens reduce energy intake by 550 kcal per day without calorie counting d Both regimens produce similar reductions in insulin resistance and oxidative stress

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Objective This study compared the effects of alternate‐day fasting (ADF) with those of daily calorie restriction (CR) on body weight and glucoregulatory factors in adults with overweight or obesity and insulin resistance. Methods This secondary analysis examined the data of insulin‐resistant individuals (n = 43) who participated in a 12‐month study that compared ADF (25% energy needs on “fast days”; 125% energy needs on alternating “feast days”) with CR (75% energy needs every day) and a control group regimen. Results In insulin‐resistant participants, weight loss was not different between ADF (−8% ± 2%) and CR (−6% ± 1%) by month 12, relative to controls (P < 0.0001). Fat mass and BMI decreased (P < 0.05) similarly from ADF and CR. ADF produced greater decreases (P < 0.05) in fasting insulin (−52% ± 9%) and insulin resistance (−53% ± 9%) compared with CR (−14% ± 9%; −17% ± 11%) and the control regimen by month 12. Lean mass, visceral fat mass, low‐density lipoprotein cholesterol, high‐density lipoprotein cholesterol, triglycerides, blood pressure, C‐reactive protein, tumor necrosis factor α, and interleukin 6 values remained unchanged. Conclusions These findings suggest that ADF may produce greater reductions in fasting insulin and insulin resistance compared with CR in insulin‐resistant participants despite similar decreases in body weight.

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Background: Time restricted feeding is a form of intermittent fasting where participants shorten the daily window in which they eat. Aim: This is the first study to examine the effects of intermittent fasting on changes in the gut microbiome. Methods: Adults with obesity ( n = 14) participated in a daily 8-hour time restricted feeding intervention (8-hour feeding window/16-hour fasting window) for 12 weeks. Fecal microbiota were determined by 16 S rRNA (ribosomal ribonucleic acid) gene sequencing of stool samples. Results: Body weight decreased ( P < 0.05) by -2 ± 1 kg. Gut microbiota phylogenetic diversity remained unchanged. The two most common phyla were Firmicutes and Bacteroidetes accounting for 61.2% and 26.9% of total abundance at baseline. No significant alterations in the abundance of Firmicutes, Bacteroidetes, or any other phyla were detected after 12 weeks of time restricted feeding. Conclusions: Time restricted feeding did not significantly alter the diversity or overall composition of the gut microbiome.

This review aims to summarize the effects of intermittent fasting on markers of cardiometabolic health in humans. All forms of fasting reviewed here—alternate-day fasting (ADF), the 5:2 diet, and time-restricted eating (TRE)—produced mild to moderate weight loss (1–8% from baseline) and consistent reductions in energy intake (10–30% from baseline). These regimens may benefit cardiometabolic health by decreasing blood pressure, insulin resistance, and oxidative stress. Low-density lipoprotein cholesterol and triglyceride levels are also lowered, but findings are variable. Other health benefits, such as improved appetite regulation and favorable changes in the diversity of the gut microbiome, have also been demonstrated, but evidence for these effects is limited. Intermittent fasting is generally safe and does not result in energy level disturbances or increased disordered eating behaviors. In summary, intermittent fasting is a safe diet therapy that can produce clinically significant weight loss (>5%) and improve several markers of metabolic health in individuals with obesity.

SummaryObjectiveAlternate day fasting (ADF) is a popular weight loss regimen. Whether carbohydrate restriction can enhance the weight loss achieved with ADF remains unclear. Accordingly, this study examined the effect of ADF combined with a low‐carbohydrate diet on body weight and metabolic disease risk factors.MethodsAdults with obesity (n = 31) participated in ADF (600 kcal “fast day” alternated with an ad libitum “feast day”) with a low‐carbohydrate background 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.ResultsBody weight decreased (−5.5 ± 0.5%; P < .001) during the weight loss period (month 0‐3) but remained stable (P = .57) during the weight maintenance period (month 4‐6). Net weight loss by month 6 was −6.3 ± 1.0%. Fat mass was reduced (P < .01) by month 6, while lean mass and visceral fat mass remained unchanged. Total cholesterol and low‐density lipoprotein (LDL) cholesterol levels decreased (P < .05) by −6 ± 2% and − 8 ± 3%, respectively, by month 6. Systolic blood pressure was also reduced (P = .03) by −7 ± 3 mm Hg. Fasting insulin decreased (P = .03) by −24 ± 8% by month 6 relative to baseline. High‐density lipoprotein (HDL) cholesterol, triglycerides, diastolic blood pressure, heart rate, fasting glucose, homeostatic model assessment of insulin resistance (HOMA‐IR), and haemoglobin A1C (HbA1c) remained unchanged.ConclusionsThese findings suggest that ADF combined with a low‐carbohydrate diet is effective for weight loss, weight maintenance, and improving certain metabolic disease risk factors such as LDL cholesterol, blood pressure, and fasting insulin. While these preliminary findings are promising, they still require confirmation by a randomized control trial.

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