UK politician Tom Watson left a lot of people scratching their heads today when he revealed he has lost 45 kilograms and 鈥渞eversed鈥� his type 2 diabetes on a low-carb diet. Although it was coupled with an exercise regime, this is not supposed to be a healthy way to eat. What鈥檚 going on?
Watson鈥檚 impressive achievement cuts to the heart of the biggest controversy in nutrition science today. Mainstream medicine says diets should be low in fat and high in starchy carbohydrates such as bread, potatoes and pasta.
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People should especially shun saturated fat, from red meat and dairy, because this is said to raise cholesterol and so the risk of heart disease. This is the advice from and in most western countries.
According to this orthodoxy, weight depends on the balance between calories in and calories out. If you want to lose weight you have no option but to double down on avoiding fat because it has over twice the calories per gram as the other two main food groups, carbs and protein.
Medicine鈥檚 dirty secret
If people have a low-fat and low-calorie diet they do lose weight 鈥� and if they had type 2 diabetes to start with, their blood sugar levels may well return to normal. But medicine鈥檚 dirty secret is that this is not the only method.
Watson鈥檚 alternative approach is not a new one; it has gone in and out of fashion over the years, known variously as Banting, Atkins or the keto diet. It involves minimising all carbs, whether sugar or starch 鈥� including wholegrain sources like brown rice. Instead, people fill up on protein and fat-rich foods like meat, fish, cream and butter.
Even fruits are shunned because of their sugar, although vegetables help to bulk out meals. This is why supermarket shelves these days proffer carb substitutes like cauliflower 鈥渞ice鈥� and courgette 鈥渟paghetti鈥�. One bonus is people don鈥檛 need to calorie count.
It really shouldn鈥檛 work 鈥� and yet it does. Randomised trials show that it鈥檚 at least 鈥� in fact some trials suggest it鈥檚 better. All that saturated fat doesn鈥檛 even raise people鈥檚 cholesterol.
The explanation is unclear. Some advocates say it鈥檚 because the body no longer needs to make as much insulin, the hormone the body uses to cope with an influx of sugar. Certainly the low-carb approach is popular among people with type 2 diabetes 鈥� a disease of high blood sugar.
Another theory is that low-carbing forces your body to get calories by burning fat instead of sugar, which has a slew of downstream effects on the metabolism.
Sceptics say low-carbing only works because the monotony makes people eat fewer calories overall, even though they鈥檙e not counting them. But when people go short of calories they generally get hungry, and one thing low-carbers like to shout about is that they鈥檙e not hungry.
For now, the explanation for the success of low-carb dieting is unclear. But it certainly seems time for mainstream medicine to acknowledge that there is more than one way to lose weight. Watson has said he will set up an expert panel to look into ways to respond to the UK鈥檚 burgeoning diabetes epidemic. If so, there could be interesting times ahead for nutrition science.
