The Truth about low carb, high protein and fat ketogenic Diets

Barely a year goes by without the ‘return of the high protein, high fat, low carb diet’ in various disguises. It was invented by Dr William Harvey in the mid 1800’s, and first made popular by William Banting in 1864. But it wasn’t until Dr Robert Atkins turned the basic principles into his Atkins Diet in the 1970s, which then became a best-seller in 2002, that the principle of avoiding carbs, and eating high fat and protein became a popular weight loss approach.

This has mutated into various forms from the South Beach Diet in California to the Dukan Diet in France, the Real Meal Revolution in South Africa and the Total Wellbeing Diet in Australia. It is not dissimilar to the paleo or Stone Age diets which shun grains and other carbs in favour of lots of meat plus vegetables, on the basis that it is what our ancestors ate.

The central idea is that, by eating lots of fat and protein, and virtually no carbs, the body’s metabolism switches from burning glucose to burning ketones and goes into a state of ‘ketosis’. Think of ketones as a back-up fuel when times are hard – it’s what we survive off when we burn our own fat in times of starvation. Since fat converts most easily into ketones, low-carb diets recommend lots of high fat meats and dairy products, despite neither being part of our ancestors diet.

There have been lots of studies that show:

  • that it works for weight loss, but no better than my kind of low GL diet, which advocates a bit more protein, less and the right kind of low GL carbs
  • that it works for diabetes reversal and lowering blood fats (triglycerides made from glucose)
  • that it’s not the ketosis that makes the diet work, but the reduction in calories.But longer term studies (1 year+) don’t tend to show a benefit over other less extreme low GL (glycemic load) dietary approaches.

For example, a review of 19 trials comparing low carb versus balanced diets concludes, ‘There is probably little or no difference in weight loss and changes in cardiovascular risk factors up to two years of follow-up when overweight and obese adults, with or without type 2 diabetes, are randomised to low carb diets and isoenergetic (calorie) balanced weight loss diets.’ Another trial comparing four diets – high carb, high GI foods; high carb, low GI foods; high protein, high GI foods; high protein, low GI foods – concludes:‘Both high-protein and low-GI regimens increase body fat loss, but cardiovascular risk reduction is optimised by a high-carbohydrate, low GI diet.’ My low GL diet may produce the best of both worlds, being medium carb, slightly higher protein, but low GL.

Low carb advocates say that the fact that a low-carb diet doesn’t produce more weight loss than other diets on the same calories isn’t the point – eating more fat and protein makes you fuller so you eat less. I’m sure this is true but the same can be said for low GL diets. Also, studies comparing a low GL diet with a high GL diet do show more weight loss on the same calories, as well as reporting substantial reduction in hunger. Also, this low GL approach is very effective for reversing both diabetes and cardiovascular disease. (I summarise these in my report gl-scientific-evidence.)

One of the selling points of the low carb diets, if you get past the agonising first week, which is how long it often takes to get into ketosis, is that you get rapid weight loss in the first two weeks. But much of this is false. When you starve the body of glucose you have to burn off glycogen stores (glucose plus water) and therefore rapidly lose weight as water. But, unless you are going to stay ketogenic for the rest of your life, this comes back.

Given that lots of people are on a variation of a low-carb diet precisely because it does work for weight loss and diabetes reversal (and/or they like meat), my concern...

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