Intermittent fasting, in which individuals fast on consecutive or alternate days, has been reported to facilitate weight loss and improve cardiovascular risk. This review evaluates the various approaches to intermittent fasting and examines the advantages and limitations for use of this approach in the treatment of obesity and type 2 diabetes.
Intermittent fasting can be undertaken in several ways but the basic format alternates days of ‘normal’ calorie consumption with days when calorie consumption is severely restricted. This can either be done on an alternating day basis, or more recently a 5:2 strategy has been developed (Figure 1), where 2 days each week are classed as ‘fasting days’ (with <600 calories consumed for men, <500 for women). Importantly, this type of intermittent fasting has been shown to be similarly effective or more effective than continuous modest calorie restriction with regard to weight loss, improved insulin sensitivity and other health biomarkers.1,21
Obesity comprises multiple genetic, metabolic and behavioural abnormalities that complicate treatment. Most pharmaceutical therapies that promote weight loss have been discontinued, and at the time of writing the only licensed anti-obesity drug on the UK market is orlistat.1 Increasing numbers of obese individuals are undergoing bariatric surgery, but this remains a restricted minority treatment.36 The mainstay of treatment for obesity therefore remains lifestyle intervention based around dietary changes37⇓⇓-40 which generally form the first step in any weight loss programme.
Intermittent fasting is known to be useful in the treatment of intractable obesity,41 and morbidly obese individuals.42 Original treatment regimens were based upon intermittent starving as opposed to restricting calories43,44 a harsh regime that must have challenged adherence. Despite the seemingly strict nature of the fasting days intermittent fasting has a generally good adherence record and can cause significant reductions in body weight in individuals with obesity,45-46 suggesting that this is a clinically relevant therapeutic approach.
“Intermittent fasting: a dietary intervention for prevention of diabetes and cardiovascular disease?