Intermittent Fasting
Intermittent Fasting
Now that the holiday season is a distant memory, we might all need to shake things up in the health department.
Intermittent fasting (IF) is an umbrella term for various diets that cycle between periods of food restriction (or fasting) and non-fasting. The period of restriction may be hours or whole day, and may be fluid-only or significantly reduced food intake (calorie restriction). The period of non-fasting may be a feast, normal eating, or quite mindful consumption, depending on the protocol.
The goals of intermittent fasting include not only weight loss, but disease prevention and treatment. Some people even employ therapeutic fasting in an attempt to slow the effects of ageing.
Traditional calorie restrictive (CR) diets can dramatically improve metabolic health and other markers of health and longevity. Intermittent fasting regimes (in animals) also increase longevity, and reduce the risk of CVD, metabolic dysregulation and cognitive dysfunction (Horne et al. 2015). The effects in humans, while promising, are less well researched.
As the food restriction of IF is less frequent, but more intense, than CR diets, some find compliance more achievable. Therapeutic fasting is emerging as a preferred and effective alternative for sustained weight loss and other health outcomes.
TYPES OF INTERMITTENT FASTING
5:2 Fasting - involves adopting a reduced calorie regimen on two (usually) non-consecutive days a week. Reducing to one-day/week fasting for maintenance.
Alternate Day Fasting - eating every other day. More restrictive than the 5:2 diet, possibly requiring greater lifestyle modifications to compensate for low energy days, and therefore, more challenging to sustain.
Time Restricted Feeding (TRF) – confines food access to an 8-12 hour window during the active phase (fasting for 12+ hours/day). Fasting for religious reasons such as that observed by Moslems during the month of Ramadan, restricting dietary intake between sunset and sunrise, is similar to TRF.
16:8 fast - 8-hour active phase (say 10am-6pm). There is no calorie restriction, which may aid compliance. It may be useful for those who struggle to reduce daily food intake without side effects, or without inhibiting activity levels. It is also used in cancer treatment when prolonged fasting is inadvisable.
How does it work?
The mechanisms for the benefits of IF are not entirely known, but are thought to involve the body’s use of fat for energy during fasting, reducing adipose mass and resulting in small, short-term reduction in risk after each fasting episode.
Low carbohydrate/ketogenic diets rewire energy metabolism to utilise ketones as an energy source rather than glucose. Fasting for more than 12 hours also utilises fat for energy. These diets mimic many of the metabolic and anti-inflammatory properties of Calorie Restriction, including reduced blood glucose, insulin, and IGF-1, fatty acid oxidation and generation of ketones. The ketogenic diet has been used successfully in type 2 diabetes.
Nutritional stress during fasting results in cellular repair, functional optimisation and metabolic rejuvenation, impacting the aging process. Our modern-day 24hr lifestyle, through the use of artificial light and technologies, causes disruption to the natural activity-rest cycle, circadian rhythm, and natural feed-fast cycle. This can contribute to metabolic disease and my also accelerate the aging process. Shift work and sleep deprivation have been linked to predisposition to cancer, obesity and metabolic syndrome.
The results
In humans Intermittent Fasting can have a wide range of effects on metabolic markers and risk factors for diseases, including: reducing body (& visceral) fat, blood pressure, triglycerides, LDL cholesterol particle size, LDL cholesterol, C-reactive protein; increasing insulin sensitivity, HGH (facilitating lipolysis and fatty acid release for energy), red blood cell count. There are no clinically significant effects on glucose levels
IF has been associated with lower odds of CAD (Coronary Artery Disease) and diabetes, has been shown to reduce inflammation, enhance immune function, and have additive and possibly synergistic effects when combined with drugs. It has been shown to enhance cancer treatment with both chemotherapy and radiation therapy and there are potential applications for IF in inflammatory disease - significantly reducing symptoms of rheumatoid arthritis and reducing inflammatory markers in asthma sufferers.
Time Restricted Fasting has been associated with reduced breast cancer risk. Positive anecdotal reports from those following the 5:2 diet include weight loss, improved asthma symptoms, increased energy, mood enhancement, reduced impact of fibromyalgia, epilepsy management, reduced blood pressure, improved fitness levels, reduction of skin irritations and improvements with glucose levels.