Could intermittent fasting hold the key to healthy weight maintenance, asks Rod Tucker
Plagued by guilt from the consequences of over-indulgences during the festive period, many of us take one look at our expanded girth and vow to shed those extra pounds. The desire to kickstart health by losing weight at the start of the year is a common pronouncement. In fact, a YouGov poll in 2019 found that 44% of us made it a New Year’s resolution to lose weight. Sadly, that same survey revealed how 64% of people did not manage to keep their resolution!
Dieting is especially hard because there are myriad different options, from low carb and low fat to low calorie or high protein and it be difficult to know which one to choose. Moreover, the term ‘diet’ is somewhat punitive: we are made to forego the foods we love in an effort to lose weight.
Sadly, the reality of dieting is such that for many people, the weight returns with a vengeance and a third to two thirds of dieters regain more weight than they lost on their diet. Rather than trying to decide upon particular dieting approach, what if we could continue to eat what we wanted but simply change the times at which we ate and still lose weight? This is the basic principle behind intermittent fasting (IF).
The concept of fasting has been practiced for centuries and incorporated into religions such as Islam, in which Muslins fast every year for the month of Ramadan. In recent years there has been renewed interest in the idea of fasting as a means of weight reduction.
A 2019 study found that just four weeks of alternate day fasting led to a 4.5% reduction in body weight in non-obese individuals. Nevertheless, the regime was harsh and participants could only consume water and unsweetened black or green tea or coffee on fast days – though they were free to eat what they wanted on feasting days.
The study found that in addition to loss of body fat, there were also reductions in blood pressure and heart rate. Although not eating for a whole day might seem extreme and difficult to maintain, there are several other intermittent fasting regimes include 12:12, where you only eat within a 12 hour period, 16:8 (eating within an 8 hour window) and so on. One particular regime that has become popular is the 5:2 diet, in which a person eats normally for five days and has no more than 600 calories on the fast days.
It therefore seems that, potentially, IF is the holy grail of dieting: simply alter the feeding time window and still lose weight without the need to restrict particular foods. Furthermore, once adapted to the eating regime there is no reason why a person couldn’t continue indefinitely.
But are there health benefits from adopting an IF routine? This was the subject of a recent review article in the New England Journal of Medicine (NEJM). The authors start by describing how IF was common among our ancestors, not through choice but necessity. Today, many of us consume three meals a day plus a few snacks but our ancestors ate only after a successful hunt and went hungry in-between. These fluctuations in the availability of foods lead to an evolutionary adaptation termed a metabolic switch. Under normal circumstances, our primary source of energy is glucose but when this is scarce, flipping the switch leads to the burning of stored fats instead.
What was interesting in the NEJM review is how emerging evidence points to IF being associated with a host of physiological improvements that are not directly related to weight loss. These include better cognitive functioning, improved cardiovascular markers (eg blood pressure, lipid levels), delaying neurological diseases such as Alzheimer’s and improving asthma, arthritis and even multiple sclerosis. There is even the potential to reduce the growth of cancer cells though further work needs to be done. Some preliminary work also suggests that IF is suitable for patients with type 2 diabetes leads to weight loss, reduced glycated haemoglobin levels and avoiding the need for insulin.
The majority of our patients (and pharmacists) probably put on a few pounds during the holiday periods because we relax and eat what we want. Intermittent fasting appears to offer many additional health benefits to weight loss and should not be advocated as a short-term but as a healthy lifestyle choice. But perhaps most important of all is that IF still allows us to have our cake so long as we are careful when we eat it.