I believe that what represents an ideal diet varies from person to person, but one thing I’m clear about is that many health professionals and even our Governments advise intakes of carbohydrate that are greater than is good for us. In particular, while starchy carbohydrates such as bread, potatoes, rice, pasta and breakfast cereals have for a long time been promoted as wholesome, nutritious and healthy, the reality is that they tend to be disruptive for blood sugar and insulin levels in a way that can predispose to all sorts of problems including weight gain, type 2 diabetes and cardiovascular disease.
Those who traditionally criticise low carbohydrate diets have often done this on the basis of safety. This is ironic because there is actually quite a stack of evidence which shows that lower-carb diets generally lead to significant improvement in certain markers for disease including blood fat levels and measures of blood sugar status.
One such study was published this very day in the on-line journal Nutrition and Metabolism. This study took 50 overweight or obese individuals (average body mass index 33.6) and randomised them to eat one of two test diets [1]. One of these diets was relatively low in protein and rich in carbohydrate. The other was higher in protein (1.6 g of protein per kg of body weight) and lower in carbohydrate (less than 170 g of carbohydrate compared to more than 240 g in the other diet). Both diets were calorie-restricted, supplying 500 calories less per day than the amount estimated to be required to maintain stable weight. The study lasted for four months.
At the end of the study, the higher protein, lower carb eaters had lost more weight (9.1 per cent compared to 7.3 per cent of those eating more carb and less protein), though the difference was not statistically significant. The group eating less carb lost more fat than the higher carb consumers, and this difference was statistically significant (8.7 per cent v 5.7 per cent).
The improved fat loss is important here, because it serves to remind us that gross weight loss tells us nothing about what actually has been lost. For individuals who are carry extra fat, fat is the thing that is what needs shifting, and the higher protein, lower carb diet was the clear winner here. Why? Well part of the explanation may lie in the fact that the lower carbohydrate diet, in theory at least, should have led to lower levels of the hormone insulin, which happens to be the chief hormone responsible for fat deposition in the body.
Evidence which supports this concept comes from the finding in this study that the lower carb diet led to lower insulin levels after eating compared to the higher carb diet. The difference was statistically significant. Less insulin might not only mean less fat, it may well mean lower risk of type 2 diabetes in time too.
Other statistically significant benefits of the higher protein, lower carb diet were seen in the levels of triglycerides, HDL-cholesterol and LDL-cholesterol.
The authors of this study conclude: A weight loss diet with moderate carbohydrate, moderate protein results in more favorable changes in body composition, dyslipidemia, and post-prandial INS [insulin] response compared to a high carbohydrate, low protein diet suggesting an additional benefit beyond weight management to include augmented risk reduction for metabolic disease.
Common sense dictates that a generally healthy diet will be one that is similar to the diet we ate for longest in terms of our evolution on this planet. Why? Because that’s the diet we evolved to eat, and it’s therefore the diet we’re most likely to be best adapted to. It is perhaps interesting to note that primitive diets have been found to considerably less carbohydrate and more protein than the sort of diet we typically eat now [2]. It is perhaps no wonder that rates of obesity and type 2 diabetes are rising like they are. And there’s certainly an argument for returning our diet to something more primal in nature
References:
1. Walker Lasker DA, et al. Moderate carbohydrate, moderate protein weight loss diet reduces cardiovascular disease risk compared to high carbohydrate, low protein diet in
obese adults: A randomized clinical trial. Nutrition & Metabolism 2008, 5:30
2. Cordain L, et al. Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets. Am J Clin Nutr. 2000 Mar;71(3):682-92
