Intermittent fasting is a technique whereby calorie intake is reduced or stopped for a period of time. Although this technique is synonymous with the dieting and fitness industries, this method is used in both religious practices and in clinical populations to beneficially affect parameters of disease and ill health. Often, this form of fasting is used in the period including sleep by avoiding a breakfast meal to extend the period of the fast to potentially 12-14 hours.
Several large studies have identified potentially beneficial applications of intermittent fasting in special populations such as type 2 diabetics and obese individuals. Fasting for periods of time in the day has an effect on your metabolism by affecting the utilisation of fuel for sustaining body functioning (known as your basal metabolic rate). Normally, the human body uses glucose for higher brain functioning and activity of a moderate to low intensity. However, resting measures of substrate utilisation (such as during sleep) indicate the main source of energy is through use of fat. The theory behind intermittent fasting is that manipulation of feeding and resting times may increase the chance of fat use for a greater period over the day, permitting greater loss of fat mass.
Periods of prolonged fasting provide an opportunity for fat use to occur as levels of the glucose regulating hormone insulin fall. In a Harvard report, intermittent fasting in obese men promoted improved factors related to diabetes, suggesting an improvement in the features of insulin resistance. Individuals must however be aware of certain fads and trends which allow a ‘eat what you want’ approach during daylights hours of feeding, as this promotes the likelihood of intake of food groups prone to causing obesity and macronutrients in excess quantities i.e. fats and refined carbohydrates.
As with any topic concerning scientific introspection, studies exist which refute findings and beneficial effects of intermittent fasting. Several rodent and human studies have found reductions in lean body mass and fat mass concurrently yet documented an increase in fat mass once a ‘regular’ diet has been restarted, demonstrating the need for diet counselling and awareness in a population. Furthermore, the and regulation of this technique in extreme populations (athletes/clinical populations) is not without its dangers, and those looking to try this approach must consult a healthcare professional before commencement.
Manipulation of dietary measures alone often provide limited effect, and one can experience greater, sustainable results through a combination of diet and physical activity. The uptake of physical activity is useful to increase daily energy expenditure, and a consensus in the scientific community of output greater than input are generally recommended. In the realm of dieting and health, caution must be exercised as to the quality and source of information, and thus individuals should generally consult doctors or peer-reviewed information to ensure the reliability of information. Indeed, some of the heterogeneity in the studies into intermittent fasting are due to great variation in individual response, demonstrating a need for personal experimentation and trial of various methods to identify an appropriate, individualised approach. Furthermore, a yo-yo approach to extremes of dieting has implications for metabolic damage and thus individuals should avoid severe approaches to weight loss and body composition changes and should be encouraged to regard intermittent fasting as part of a long term approach.
A ‘healthy lifestyle’ can sometimes seem ambiguous, but small changes can often have a great effect. Maintaining at least 150 minutes of physical activity per week (through walking, climbing stairs, shopping etc) and changing your diet to a more Mediterranean approach with less high fat, high sodium foods is a great way to reduce your risk factors for cancer, cardiovascular disease and high blood pressure.