Matthew Capehorn, clinical director of the UK’s National Obesity Forum, plays Devil's Advocate to weight up the benefits of taking it quick.
In weight-loss lore, tortoises end up leaner than hares. Crash diets, we’re told, are not sustainable in the long term – a juice cleanse or month of cabbage soup might help you shed the kilos, but without tackling the underlying reasons, you pile it back on the minute you go back to solids.
But the lore is an ass. The simple fact is that crash diets – even the ones named for the book-touting “gurus” who devise them – do work. From Dukan to Atkins via South Beach and Beverly Hills, the majority of rapid fat-loss plans take carbs out of your daily fare to cut your gut with clinically proven success.
I’m not saying that they are particularly pleasant, mind you. Our societal reliance on carbohydrates as an energy source means that cutting them out almost entirely leads you to consume far fewer kilojoules over the course of the day. So you’re hungry. Stick with it for a few days, though, and your body will shift into a state called ketosis – burning fat rather than food for energy – which has the handy side-effect of dulling your appetite after a week or so.
That crash diets make this sort of impact is the aim but, staying with physics, the force of that impact dissipates greatly over even a short time period. Diet for more than a few weeks and the effort-to-reward graph plateaus, with your initial rate of weight loss levelling off. More crucially, on returning to your normal way of eating, the results simply don’t stick. To capitalise on the benefits of a crash without the bounce back, you need to alter your “set point”.
According to the set point theory, your body gets used to the mass it normally functions at and calibrates your metabolism and appetite accordingly to keep you within a small margin of this weight. So you need to exercise if you want to exist at a lower weight long-term.
While it’s unwise to step into the squat rack when you’re low-carbing, increasing daily activity – whether that’s walking more or a bedroom body-weight routine – will stop your body eating muscle instead of fat to fuel itself. When you’ve harvested a diet’s weight-loss benefits, hitting the gym with equal zeal will see you stay lean for life. So for once, heed the screaming headlines and crash away.
The Devil’s Details
1. Curb Carbs
Tulane University School of Public Health found that low-carb dieters lost more over a year than those on a low-fat plan.
2. Hang Hunger
The ketones released by burning fat, not sugar, increase hunger-fighting hormones. More fibre also aids fullness.
3. Mass Appeal
Still, a Lancet study found 81 per cent of rapid dieters lost over 12.5 per cent body mass, compared with 50 per cent of dieters on a more gradual plan.
4. What Supp
Protect your muscles: taking BCAAs pre-workout helps to reduce catabolism, which chews up hard-earned gains.