Intermittent fasting has become a trendy means of losing weight, some also associating it with several health benefits including lowering the risk of chronic disease.
There are several methods of intermittent fasting. Despite the time of day in which you fast, you will (surprise, surprise) be eating less! A meta-analysis of intermittent fasting in comparison to long term energy restriction for weight loss found neither to be superior (Headland, et. Al 2016). As boring as it sounds – the message of calories in vs. calories out still reigns true.
|5:2||2 days of low energy intake (500 cals for women, 600 for men). 5 days of energy intake to maintain weight.|
|16/8||Fast for 16 hours. Restricting eating ‘window’ to 8-10 hours.|
|Eat-Stop-Eat||24 hour fast, once or twice a week|
|Alternate day fasting||Varies from complete fast to a small reduction of calories every second day|
|Warrior Diet||Fast during the day, huge meal at night|
|Spontaneous meal skipping||Skip meals when convenient or not hungry|
But what about health claims? Studies among normal weight participants and in animal models have shown benefits of intermittent fasting in reducing visceral fat stores, improving insulin resistance and manipulating metabolism (Harvie & Howell, 2016). There are also studies that associate energy restriction with preventing cardiovascular disease, diabetes, dementia and functional decline. However, well-designed human studies are limited and therefore it could be suggested that the health benefits of energy restriction simply stems from the known health benefits of losing weight. The popularity of intermittent fasting warrants further study in understanding the long-term effects on health independent of weight loss.
Are there dangers? There are certainly psychological concerns that intermittent fasting favours erratic eating behaviours being a trigger for binge eating. There is also the worry of athletes being able to successfully follow the diet as adequate nutrition is needed to support training and recovery. Restricting calories may also lead to cutting out food groups and therefore vitamins and minerals necessary for general health.
EVIDENCE to PRACTICE.
- Like any diet, intermittent fasting can assist in weight loss if it is consistent. Ask yourself if this diet is something you can commit to long term.
- As there is no specific prescription for intermittent fasting that has been proven to be more effective, manipulate the diet to suit you. Simply having a smaller dinner twice a week such as yogurt, crackers with cheese or soup will assist in losing weight.
- It’s important to incorporate plenty of nutrient dense foods on low calorie days including vegetables, salads and lean protein. A carefully planned diet will ensure you meet vitamin and mineral requirements for good health.
- Restricting energy intake on heavy training days is a recipe for decreased performance and burning through muscle as an energy source. Keep low calorie days to recovery or light training days.
- Intermittent fasting is not for everyone. Weight loss is not a one fits all approach. Your Dietitian has a toolbox bursting with strategies that may work 100% better FOR YOU.
Gunnars, K. (2017). 6 Popular Ways to do Intermittent Fasting. Authority Nutrition via Healthline. Accessed online 23.10.17
Harvie, M and Howell, A. (2016). Potential benefits and harms of intermittent energy restriction and intermittent fasting amongst obese, overweight and normal weight subjects – a narrative review of human and animal evidence. Behavioural Sciences 7 (4). Accessed online 23.10.17
Headland, M. Clifton, P. Carter, S and Keogh, J. (2016) Weight-Loss Outcomes: A Systematic Review and Meta-Analysis of Intermittent Energy Restriction Trials Lasting a Minimum of 6 Months. Nutrients. June 8(6): 254. Accessed online 23.10.17
Sports Dietitians Australia. (2017). How Intermittent Fasting Affects Your Performance. Accessed online 23.10.17