4 Nov 2012
The latest diet buzz is a regime called Intermittent Fasting (also known as the 5:2 Diet or Alternate Day Fasting). Incredibly, you can eat whatever you want most of the time. Does it work? Well, according to Dr Michael Mosley who followed it as part of his investigation for BBC2’s Horizon programme in August, it does. He lost nearly a stone and 25% of his body fat in 5 weeks. But it’s not really a fast – you eat what you want five days a week, then twice a week you restrict yourself to just 500 (women) or 600 calories (men). The idea is that it reduces levels of IGF-1 (insulin-like growth factor 1, which leads to accelerated ageing), switches on DNA repair genes and reduces blood pressure, cholesterol and glucose levels.
Fears about people bingeing on cake and pizza are unfounded. According to Mosley, most dieters, find that they are happy to consume around 2,000 calories — the recommended daily intake for women (2,600 for men) — on non-fasting days.
And therein lies the secret of weight loss. You eat less. Over a week, if you eat 500 – 600 calories on 2 days, 2000 – 2500 on 5 days, you end up averaging a calorie deficit of around 3500 calories, which happens to equate to a 1 lb weight loss (Do the math, as they say!). And, crucially, it’s a regime that many find easy to stick to. If you only have to apply the calorie brakes on a couple of days a week, you won’t feel as if you’re constantly on a ‘diet’ and tempted to throw in the towel. It works because it’s do-able.
But I worry about this diet, despite its ease of use. Modified fasting may sound fairly harmless but there is limited evidence of its efficacy in long-term human trials (so far we have been going on animal data). And I worry that already-slim people and anorexics will latch on to the concept and take it to an extreme. Why not drop those 500 calories altogether or extend the fast? It should also be kept well away from children, pregnant women and diabetics. Would it work for athletes? Not an issue – they’ll quickly learn that they can’t fast and train!