Low carb weight loss diets - do they really work?

In my experience as a sports nutritionist, fitness instructor and competitive athlete, I know that low carbohydrate (CHO) diets are not the long-term answer to weight problems. Before you embrace the new low CHO gospel, take a reality check!

If you lose weight on a low CHO diet, it's because of the low calorie count

Most provide between 1,000 and 1,200kcal per day. Research at Ball State University, Indiana, compared a 1,200 kcal Zone diet (40% CHO, 30% protein, 30% fat) with a 1,200kcal traditional diet (60% CHO, 15% protein, 25% fat). Both produced equal amounts of weight loss but the Zone diet raised harmful triglyceride levels by 14 mg/dL. The American Heart Association has recently warned against high protein, low CHO diets for increasing heart attack risk and producing only short-term weight loss. People are highly unlikely to overeat high fat and high protein foods. If you take out virtually all the sugar and starch you automatically restrict the foods you can eat and end up consuming fewer calories. In practice, portion sizes in these diets are terribly small. It''s a simple negative energy balance equation!

Threat of ketosis and loss of muscle caused is a concern for regular exercisers

A calorie deficit greater than 15% or weight losses greater than 0.5kg per week results in loss of muscle and a drop in the metabolic rate. Okay, you get weight loss but the price to pay is muscle wasting. Result: a worse body composition and worse body shape! Look at the emaciated physiques of those Hollywood stars - all skin and bone. On a low CHO diet glycogen stores quickly deplete, causing lethargy, a drop in performance, low energy levels and mounting hunger. Carbohydrate is a major fuel for all types of exercise. You cannot ignore the decades of quality research proving that high muscle glycogen levels promote optimal athletic performance.

Low CHO diets are restrictive and appealing to those with slightly obsessive personalities

Some people love strict eating rules ("I can''t eat bread", "I''m not allowed to eat carbohydrate after 5 o''clock") and the ensuing social attention. What the diet gurus have cashed in on is the novelty value of the diet. A "different" eating system that goes against the grain of established science appeals to certain personalities and that, in itself, is motivating. It''s hardly surprising that these diets have captured the imagination and stomachs of high-profile celebrities.

There is little scientific support for the theory behind low CHO diets

The logic that too much carbohydrate causes overproduction of insulin, which then promotes fat storage has been criticised by eminent researchers, including Dr Gerald Reaven, a professor emeritus at Stamford University School of Medicine, California, He states that it is not the insulin that makes people put on weight; the opposite is more likely to be true. Many leading researchers have found errors regarding both hormonal action and metabolism in the Zone diet and found absolutely no evidence that supports them (eg, Cheuvront SN (1999), The zone diet and athletic performance, Sports Medicine, 27 (4): 213-228.).

Messages need to be more precise

Terms such as "high carb" and "high protein" can be interpreted as a licence to eat huge portions without any check on calories. "High protein" is equally misleading as the protein content of many low CHO diets is about right; only the carbohydrates are taken out.

In summary, I believe low CHO diets are just low-calorie diets given a new spin. If you are prepared to eat fewer calories you''ll lose weight. However, these diets are difficult to sustain in the long-term because they are not very practical for most people. There are several potential dangers - physiological and psychological - if you follow them longer than, say, a month. They could end up making you look in worse shape than before.

Courtesy of Fitness Professionals UK

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