Dr Michael Mosley’s 5:2 diet is still topping book charts worldwide. The intermittent fast involves eating normally, but sensibly, for five days a week; on the other two days, you cut your recommended daily calories to a quarter – 500 for women; 600 for men.
Yes, Associate Professor Amanda Salis, A neuroscientist with an interest in weight loss
“Periodic fasting has been practised by various religions throughout history and there’s evidence that it can be good for weight loss and health. Intermittent partial fasting such as the 5:2 diet is just one way of practicing this and, anecdotally, it has been shown to aid effective weight loss.
I’ve conducted trials on intermittent fasting and found benefits that include:
- It teaches you to find other ways of coping, and of feeling soothed and entertained besides reaching for food.
- It helps you break unhelpful habits such as grabbing snacks on the run or drinking full-cream coffees without savouring them.
- When you stop fasting and eat normally, it makes you realise how delicious a proper, nutritious meal tastes and how good it makes you feel. Once you become aware that your energy levels rise when you eat well, it’s much easier to continue eating well.
- It can help retune your ability to listen to your body’s hunger and satiety signals. You might think you’d consistently overeat on non-fasting days, and put on weight overall, but clinical research has shown that after semi-fasting days, participants tend to eat less than usual, and lose weight over time. If you’ve recently gained weight, starting an intermittent fasting diet will help the body’s “fat brake” do its job; this makes you fidgety and not so hungry in order to get you back to the “set weight” it’s become used to.
- It can be peaceful and productive. When you know your energy will be limited, you’re more likely to focus on what’s important and decline any time-wasting requests.
The 5:2 method isn’t the only way to try fasting. I fasted as an experiment by eating only during daylight hours, and lost and kept off 2kg. Anything that involves not eating or eating less for a period of time is likely to provide benefits. If you want to try fasting, do so safely. Get the OK from your doctor, try to maintain a protein intake of about 1g per kilo of body weight and keep exercising even if it’s just gentle walking. I’ve also found that it helps to fast with someone else.”
No - Kate di Prima, An accredited practising dietitian
“I don’t think people realise how limited they’ll be eating only 500 calories a day on a 5:2 diet. It means no rolls, no wraps, no cereals, no dining out...
Even if you’re capable of putting together the healthiest day possible, it would mean having two eggs and some mushrooms (no toast) for breakfast, then 60g to 80g of poached chicken and a little side salad for lunch, and a small piece of white fish with a little bit of salad for dinner. However, most people aren’t that nutritionally competent and are more likely to end up having a coffee for breakfast and lunch, then a slice of pizza for dinner.
Either way, anyone who’s trying to carry out normal activities such as working, exercising, driving or operating machinery on 500 calories would find that they’re very tired and a bit airy-fairy – which isn’t great if you have a circular saw in your hands.
Mosley says that research done by the University of Illinois in the US has shown that people who regularly fast only overindulge by 10 per cent of their normal daily intake on their non-fasting days. As food scientists, we can’t accept just one study, besides which I imagine they can’t be seeing the people I see, who can consume a packet of biscuits in one go or eat 180 per cent of their dietary requirement on a regular basis – they won’t lose weight on this diet.
The other thing that worries me is that people can reach a state of ketosis when they’re fasting (when the body has an extremely high fat-burning rate). When this happens, chemicals can be released into the bloodstream and people often report feeling fantastic. However, if you have a young girl doing that often – getting a high from controlling her weight and extending the fasting days to three or four – where might that end up?
As a mother, I believe that we should eat as a family, with parents setting a good example. At the end of the day, all you need to do to lose weight is to take 200 calories off the bottom line – it’s not that complicated.
A successful weight-loss program requires a complete lifestyle change, but all this to-ing and fro-ing on a fasting diet means that people are unlikely to change their relationship with food.
