Dieting trends (part 2): Is fasting the future?

27 Apr 2018 --- Part one of NutritionInsight’s special report into dieting trends delved into the pool of popular low-carb diets: keto and paleo. However, perhaps borrowing from the ancient religious and cultural practice of fasting could lead health seekers to their optimum diet? Taking a scientific stance by utilizing dieticians insights on the topic, NutritionInsight will take a look at intermittent fasting (IF) being used as a weight-loss diet.

Regarding keto and paleo, the pair have an active social following that is partly due to a successful social media presence and loyal adherence from particular communities such as CrossFitters. However, although the diets do have scientific backing, dietician Jennifer McDaniels warned of the dangers of cutting out entire food groups due to possible nutritional deficiencies, and of the realistic long-term weight loss maintenance of the diets. Perhaps, they may not tick all the boxes of fool-proof diet for the masses.

Fasting for fitness
Many of the latest diets and trends that are growing quickly are based upon variations of IF, for example, the 5:2 diet (normal consumption five days a week and restricted calories two days a week), the warrior diet (eating small amounts of raw fruits and vegetables during the day and one large meal at night) and the CSIRO “Flexi” diet.

Essentially, there is no one definitive intermittent fasting protocol. “IF is an umbrella term encompassing a range of diets where the pattern of calorie restriction and/or timing of food intake are altered so that the individuals undergo frequently repeated periods of fasting,” says Dr. Samefko Ludidi, Food and Health consultant, and researcher at Maastricht University, in the February edition of The World of Food Ingredients.

“In this context, it does not necessarily mean complete abstinence of food; some versions involve ‘modified fasts’ which allow a small amount of calorie intake, approximately 500-600 calories per day, such as Muslims have been doing for centuries.”

It may seem extreme to fast in a culture where eating three big meals a day is customary, but as the New York Times reports, popular manifestations of the diet, such as the 5:2, have been endorsed by celebrities from Benedict Cumberbatch to Beyonce. As with the modern low-carb diets of paleo and keto, social following and emulation probably play a role in keeping the popularity of intermittent fasting afloat.

Scientific merit
In essence, Ludidi explains, the positive benefits of IF on the body are threefold:

• “The first is glycogen depletion as a result of fasting. Depending on your level of physical actively glycogen stores are depleted after a period of about 8-12 hours fast.”
• “Second, following glycogen depletion, the body starts utilizing fat stores as an energy source.”
• “Third, fasting results in an averaging energy deficiency compared to the normal situation. The combination of these three aspects could result in weight loss.”

Furthermore, “proponents of IF claim that it can improve blood sugar levels, decrease the risk of heart disease, stroke and cancer, prevent or delay the onset of neurodegenerative diseases and even improve memory, mood and depression,” Dr. McGroarty, an Infectious Disease Specialist and Humanitarian relief, recovery and development Program Manager, notes in The World of Food Ingredients.

With such an extensive list of benefits, one could argue that no wonder the diet has reached such fashionable heights. In order to provide stable scientific backing to IF, a series of systematic scientific reviews have been conducted.

One such review, conducted by Harris et al. and published in JBI in February this year, found that amongst obese participants, intermittent fasting (alternate day fasting, fasting for two days, and up to four days per week) was an effective strategy for the treatment of obesity, as it resulted in weight loss.

However, the researchers also found that it was no more effective than continuous fasting i.e., eating 25 percent less than the “typical” daily caloric intake recommendation, in its effect on the total weight loss of obese participants. Suggesting that it is not the fasting that results in weight loss, but the overall calorie reduction.

Furthermore, a review published in Behavioral Sciences last year sought to detect both the positive and potential adverse effects of both intermittent and continuous fasting. 

Interestingly, one of the main findings of the review was the fact that the review highlighted that there is a lack of high-quality data on the topic. This is particularly salient in the effects of IF on people of normal weight, as opposed to obese.

Like most diets, IF cannot assert a “one size fits all” claim. For example, with some people following an IF regime, their metabolism will slow down when fasting in order to maintain and save energy. After they fast, they may even feel hungrier, feel greater cravings, and overeat, eventually causing them to gain back any weight that they might have lost, the February edition of The World of Food Ingredients reports.

Indeed, it seems that although the IF diets do have a strong following, and may well bring health benefits, the scientific backing that is often touted by advocates of the diet may actually be somewhat lacking when it comes to levels of weight loss itself. Other studies have found positive benefits from IF, concerning other health attributes such as endurance in exercise.   

If overall calorie reduction is indeed as effective as IF, then perhaps for certain individuals, spreading the calorie restriction across the week, with certain days being “fasting” days, may simply suit them better, and for them, IF could be a suitable weight loss regime. But as a global diet, the answer to the question, is fasting the future? may well be, no.

It could be said that once diets move quickly into the mainstream, they risk being dismissed as “fads,” or risk their benefits being overplayed and their risks downplayed. On this note, Ludidi concludes, “There is no shortcut to good health. Forget about all the holy grails. If you want to achieve results, be prepared to work for them.”

By Laxmi Haigh