Intermittent fasting — a fad or the simplest way to lower insulin?

Aim of the study: To provide an updated comprehensive evaluation of the quality and evidence association of existing studies on health outcomes related to intermittent fasting (IF).

Results: Twelve meta-analysis studies and 122 health outcome associations with IF were identified. High-quality evidence indicated significant associations between time-restricted eating (TRE) and weight loss, fat mass reduction, decreased fasting insulin and glycosylated haemoglobin levels in overweight or obese adults, as well as between the 5:2 diet and reduced low-density lipoprotein cholesterol levels. Moderate-to-low-quality evidence suggested associations between modified alternate-day fasting and improvements in body weight, lipid profile and blood pressure. Additionally, high-to-low-quality evidence showed that IF regimens effectively improved liver health in non-alcoholic fatty liver disease. This umbrella review highlights IF, especially TRE, as a promising intervention for weight and metabolic health, particularly beneficial for overweight or obese adults.

Aim of the study: fasting-based strategies (FBS) and continuous caloric restriction (CCR) are popular methods for weight loss and improving metabolic health. FBS alternates between eating and fasting periods, while CCR reduces daily calorie intake consistently. Both aim to create a calorie deficit, but it is still uncertain as to which is more effective for short- and long-term weight and metabolic outcomes.

Results: both interventions led to weight loss, with a reduction of 5.5 to 6.5 kg observed at the six-month mark. However, the results showed that FBS led to slightly greater short-term reductions in body weight (-0.94 kg, p = 0.004) and fat mass (-1.08 kg, p = 0.0001) compared to CCR, although these differences are not clinically significant. Both interventions had similar effects on lean mass, waist and hip circumference, blood pressure, lipid profiles, and glucose metabolism. However, FBS improved insulin sensitivity, with significant reductions in fasting insulin (-7.46 pmol/L, p = 0.02) and HOMA-IR (-0.14, p = 0.02). despite these short-term benefits, FBS did not show superior long-term outcomes compared to CCR. Both strategies are effective for weight management, but more research is needed to explore the long-term clinical relevance of FBS in obese populations.

Aim of the study: The aim of the present study was to investigate the effects of long-term intermittent fasting (IF) on body composition and cardiometabolic health in adults with overweight and obesity. PubMed, Web of Science, and Scopus were searched from inception to March 2024 to identify original randomized trials that investigated the effects of IF versus either a control diet (CON) and/or continuous caloric restriction (CR).

Results: Conversely, IF significantly increased high-density lipoproteins [WMD: 0.04 mmol/l] when compared with CON, but had no effects on insulin, hemoglobin A1c%, total cholesterol, low-density lipoprotein, or systolic blood pressure. Compared with CR, IF significantly reduced fat mass [WMD: -0.70 kg], body fat percentage [WMD: -0.59%], and DBP [WMD: -0.91 mmHg], and increased HDL [WMD: 0.03 mmol/l], with no other significant effects. Subgroup analyses showed that the mode of IF and intervention duration were the primary moderators of IF effects on the markers. In adults with overweight or obesity, IF and CR are comparably effective for reducing body weight and adiposity, as well as for improving cardiometabolic health markers.

Aim of the study: Intermittent fasting (IF) has gained increasing scientific and general attention. Most studied forms of IF include alternate-day fasting, modified alternate-day fasting, and time-restricted eating (TRE).

Results: In general, a decrease in fasting glucose and insulin levels is observed, together with an improved lipid profile associated with cardiovascular risk. High heterogeneity in study designs was observed, particularly in studies with TRE, small sample sizes, and short-term interventions. Current evidence shows that IF confers a range of cardiometabolic benefits in humans. Weight loss, improvement of glucose homeostasis and lipid profile, are observed in the three types of IF protocols evaluated.

Aim of the study: 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).

Results: 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.

Aim of the study: Intermittent fasting is now the third most commonly practiced diet in the USA. Yet, despite more than 225 clinical trials-including nearly 40 in patients with diabetes or prediabetes-intermittent fasting has not yet been recommended as part of the American Diabetes Association (ADA) Standards of Care or the International Diabetes Federation (IDF) Global Clinical Practice Recommendations.

Results: Moreover, intermittent fasting is as effective as calorie restriction for improving glycaemic control and does not increase the risk of hypoglycaemia when medications are adjusted using simple rules. Intermittent fasting might also reduce glycaemia in adults with prediabetes, whereas there are insufficient data to recommend its use in people with type 1 or gestational diabetes. Therefore, we argue that the evidence base has sufficiently matured to warrant including intermittent fasting in clinical practice guidelines as one of several evidence-based lifestyle options for type 2 diabetes. We also provide practical guidance for clinicians on prescribing intermittent fasting and safely managing people with diabetes.

Aim of the study: Metabolic dysfunction-associated steatotic liver disease (MASLD) is the predominant etiology of chronic liver disease and the leading factor to liver-related mortality. The endothelial dysfunction is a significant contributor to the onset of cardiovascular disease and is closely linked to MASLD.

Results: The review included seventy-three studies. Ramadan fasting might enhance MASLD, hepatic complications, and associated endothelium dysfunction and alter risk factors by facilitating weight loss, ameliorating insulin resistance, enhancing mitophagy, and inducing alterations in gut microbiota and circadian gene expression. Further studies are necessary to assess safety and efficacy of Ramadan fasting on MASLD, hepatic complications and related endothelial function. Circadian control offers a significant molecular foundation connecting Ramadan fasting to metabolic health.