The calorie conundrum
The old idea is that it was just about eating less calories. More and more studies show that eating a low glycemic load (GL) diet, designed to keep blood sugar level even, causes more weight loss on the same calories than a conventional low-fat, low calorie diet. There are two ways of eating low GL. One is by having very little carbs. Since you have to eat something that means lots of protein and/or fat instead. The other is to eat less carbs (and consequently a bit more protein) but choose the right kind of slow-release low GL/GI carbs – whole rather than refined. Both work. A low GL diet is also more effective for treating and preventing Type 2 diabetes.
But calories do count and one of the extra advantages of eating a low GL diet is that it reduces hunger – and if you’re not hungry you eat less. This is because sugar makes your blood sugar go up, which leads to weight gain, then down, which leads to carb cravings. Somewhere along this rocky road insulin levels rise, this is the hormone that is released when we eat carbs and stores them away as fat for a rainy day. The more ‘insulin resistant’ we become, the more we have to produce to control blood sugar.
Is Insulin control the key to weight loss?
High insulin is thought to be a consequence of diabetes and obesity, but animal studies suggest it might be the other way around with high insulin driving obesity.
Animals with the same diet but high or low insulin levels don’t end up the same weight. High insulin animals gain much more weight when given a high fat, calorie diet. 
There are a lot of reasons to think that controlling your insulin level is a vital key, not only to weight loss but also weight maintenance. In past issues we’ve explored the ground-breaking research that shows that reducing insulin switches on anti-ageing genes and ‘skinny’ genes, an effect that is annihilated by giving experimental animals a tiny bit of sugar.
You may recall that animals (and humans) fed very low calories are obviously skinnier, but also show all the signs of living longer. Insulin appears to be the key, not calories, for switching on these health promoting genes which supercharge your metabolism.
A case in point are two studies by Dr Michelle Harvie and Professor Tony Howell, which resulted in their book The Two Day Diet. Seduced by the animal research which showed positive gene switching when animals were given low calories every other day, they experimented with giving people a low calorie diet (600kcals) twice a week, compared to a regular low calorie diet.  The 2 day diet worked a bit better, delivering 14lbs weight loss in 26 weeks compared to 12lbs on the conventional low calorie diet.
But then they repeated the experiment, not focussing so much on calories on the two ‘down’ days but more on avoiding carbs with lots of protein and fat – a kind of part-time Atkins diet. They got a comparatively better result – nearly 9lb weight loss in 12 weeks versus 5.3lbs on the conventional low calorie diet. 
Actually, neither results are that impressive but these experiments do illustrate two points: first that you don’t necessarily need to eat less every day to lose weight, which might make diets easier to stick to, and secondly that controlling insulin with a low GL diet seems to work better than just eating fewer calories.
The dangers of high protein diets
One of the problems I have with high protein/low carb diets such as this is that they are invariably achieved by eating tons of meat and dairy products.
Variations on the Atkins diet, with high protein and fat and low carbs, have consistently been shown to be effective for short-term weight loss, but not good for maintenance/long-term weight loss. Measures of cardiovascular risk improve, as do diabetes.
Depending on the quantity of protein consumption there is an increased risk of kidney failure and reducing bone mass, contributing to osteoporosis. High meat and/or dairy diets are also associated with increased risk of cancer, especially breast, prostate and colorectal cancer.
Also, while dairy products are low GL they do raise an insulin hormone called IGF-1 (insulin-like growth factor) which is known to increases cancer risk and may switch off some of the anti-ageing benefits.
My favourite Low GL diet approach
For these reasons I have favoured a low GL diet based on eating a little more protein, mainly from fish and vegetable proteins such as beans, lentils, nuts and seeds, and less carbs as well as focussing on the low GL carbs such as wholegrain pasta, oat flakes, brown rice, quinoa and other such foods.
In head-to-head trials this kind of low GL diet has proven just as effective in losing weight short-term as Atkins-type diets but is clearly better in the long-term. An example of this is the Diogenes (Diet, Obesity, and Genes) study which was designed to assess the efficacy of diets that varied in their protein content and GL in the prevention of weight regain. In this trial, the group maintained on the low GL diet with moderately higher protein (25% of calories from protein) had the highest compliance, the lowest dropout rate, and was the only group that did not regain weight by the end of the 26-week weight maintenance intervention ......
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