Fasting diets: Do they benefit your health?

Intermittent fasting diets (IFDs) are increasingly becoming popular and of interest to both scientists and the general public in recent years. They appear to be showing promise in weight loss and seem to have potential positive health benefits.  

Daily dietary restriction in the context of a healthy balanced diet is the mainstay treatment of overweight and obesity; however, this can be difficult to achieve and maintain.  In light of this, a diet plan incorporating intermittent fasting, which is routinely practiced in Ghana for religious reasons is definitely worth our attention and exploring as a viable alternative to daily restricted dieting for weight loss.

 What are IFDs?

IFDs are also known as intermittent energy restriction (IER) or intermittent calorie restriction (ICR) diets. They involve a defined period of fasting or severe food restriction followed by periods of moderate eating. The internet and social media platforms are awash with different versions of IFDs such as 5:2 diet, The 2 day diet and Alternate day fasting diet. The main rationale behind IFDs is that they achieve the recommended reduced overall food intake for weight loss by severely restricting intake of food for a limited number of days and allowing eating more freely for the rest of the week. It is suggested that IFDs may be easier to follow than daily-restricted diets and may have greater health benefits in terms of weight loss and reducing the risk of diabetes, breast cancer and cardiovascular heart disease.

The Scientific Research Evidence

A small but increasing number of research studies have been done in humans exploring the benefits of IFDs. A UK study, published in 2011 investigated the benefits of 2-day fasting diet compared to a daily-restricted diet in overweight young women with a family history of breast cancer1. The 2-day fasting diet consisted of 2 days of severe food restriction of 650 calories/day followed by 5 days of 1900 calories/day. The daily-restricted diet advised 1500 calories /day over 7 days. Both approaches achieved similar weight loss and improvements in risk markers for cancer, diabetes and cardiovascular disease1.

Another study published in 2013 by the same team compared the daily-restricted 1500 calories diet to versions of the 2-day fasting diet with low carbohydrate 2. In this case, the 2-day fasting diet with low carbohydrate achieved better weight loss than the daily-restricted diet. Additionally, the study found continuing with a 1-day per week fasting diet after completion of 3 months of the main study, maintained the weight loss.

Few studies have also investigated alternate-day fasting diet. This involves fasting for 24 hours with no energy-containing foods or drinks followed by another 24 hours where foods and drinks are consumed freely4. The results from these studies suggest that alternate-day fasting diets can result in modest weight loss and some positive effects on risk factor markers for cardiovascular disease and diabetes 3  4 .

Bottom line: Do IFDs lead to weight loss and benefit health?

IFDs appear to promote weight loss and may improve metabolic health5. Reviews of current studies in humans suggest they are equally as effective but not superior to daily restricted diets4,5,6. In healthy adults, there is little evidence that IFDs are harmful physically or mentally or lead to unhealthy eating habits5. However, IFDs were no easier to follow than daily-restricted diets in most studies.

Despite the potential benefits of IFDs to health, there are still many unknowns such as the optimum calorie intake on fasting and non-fasting days, ideal length of fasting periods, effect on other health behaviours such as sleep and physical activity 5. The safety and effectiveness of IFDs in the long term are also yet to be established.

Our Recommendations

IFDs may have a role as an alternative diet plan in weight management for the small number of people who find daily-restricted diets difficult to follow but who are able to tolerate fasting for short periods.

However, the jury is still out on the use of IFDs in weight management and we will need further scientific evidence to determine the optimum IFD plan and its long-term safety.

Current research evidence and clinical experience informs us that successful weight loss diet plans are those that control portions and intake of calories, are palatable, promote a good rate of weight loss (up to 1 kg per week) and emphasize variety of foods and balance of nutrients for optimum body function.

Remember that, for all the latest popular quick-fix diets out there, “If it sounds too good to be true, then it probably is”. 

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