It seemed too good to be true, bacon and eggs every day if you want and still lose weight. Millions of Europeans tried The Atkins Diet and stories of dramatic weight loss were reported, but concerns regarding nutritional balance and poor long- term compliance may mean the Atkins reign is over.

Flying in the face of all official recommendations for a healthy diet The Atkins Diet advocates free consumption of fats like butter and as much meat, fish, eggs and dairy products as you like. The downside is that the consumption of carbohydrates both sweet (sugars) and savoury (starch), is severely restricted. The diet also allows only limited amounts of vegetables and especially fruits that can contain significant amounts of starch or sugars. But even though it seems unlikely, people do lose weight on this regimen - so how does it work?

Water lost initially not fat

Firstly because little carbohydrate is arriving from the diet the body starts to rely on its carbohydrate stores known as glycogen. Glycogen is bound to water in the body and this water is eliminated as the glycogen is used up. This means that the initial dramatic weight loss when starting a low carbohydrate diet is largely due to water loss not fat loss.

Appetite suppressed

Once glycogen stores have been depleted the body starts to use fat and muscle for energy. When fat is used in the absence of carbohydrate, the body produces substances called ketones, which are normally released into the urine. If ketone levels are very high, ketones may begin to build up in the blood and can be smelt on the breath - similar to nail varnish. This ketotic state can lead to nausea and fatigue but people tend to put up with it as it is an indicator of compliance with the low carbohydrates intake. Ketones contribute to suppress the appetite, as does the high protein nature of the diet, reducing spontaneous food intake. So although people are allowed to eat as much as they like, they are in fact eating fewer calories because they do not feel hungry (1).

Hard to stick to

The Atkins Diet is not in line with recommendations for a healthy diet and allows only foods that are low in carbohydrates. Although lack of choice may be a major reason why people eat less, it is also a major reason why they give up. They become bored with the food choices allowed, making it increasingly hard to stick to the diet as time goes on. It has recently been demonstrated that although people on Atkins style diets lose weight more quickly in the first 6 months compared to those on regular low-fat, calorie controlled diets, after 12 months there is no difference in success rate (2, 3). It seems that many different types of diets lead to similar long-term weight loss, the primary determinant of the success of those diets being compliance (4).

The unhealthy choice

There are many reasons why the Atkins diet is an unhealthy choice. For a start Atkins is usually high in fat, particularly saturated fat and it is not yet known what the long-term risk of this diet to heart health may be. In addition the very high protein content of the diet places a greater demand on the kidney to process and eliminate all the protein waste. It is also nutritionally unbalanced - the exclusion of carbohydrate foods including grains, fruits and vegetables means that plant-derived vitamins, minerals and fibre as well as substances like flavonoids, carotenoids and other antioxidants, are also lacking in the diet. We should be eating more, not less, of these foods which help protect us against diseases like heart disease and cancer.

Public moving on

Although initially attractive, the Atkins diet seems to get boring after a short while and does not lead to greater long-term weight loss than other diet plans. A number of scientific studies are underway or being planned to examine the long-term health effects of following such an unbalanced diet, but in the meantime its widespread popularity may already be waning. The public are moving on, sales of The Atkins Diet books and products are down. What will be the next diet phenomenon?

References

1. Astrup A, Larson T and Harper A (2004) Atkins and other low-carbohydrate diets: hoax or an effective tool for weight loss? The Lancet 364:897-899.
2. Foster GD et al (2003) A randomized trial of a low-carbohydrate diet for obesity. New England Journal of Medicine 348:2082-2090.
3. Stern L et al (2004) The effects of low carbohydrate versus conventional weight loss diets in severely obese adults: one year follow up of a randomised trial Annals of Internal Medicine 140:778-785.
4. Dansinger ML et al (2005) Comparison of the Atkins, Ornish, Weight Watchers, and Zone Diets for Weight Loss and Heart Disease Risk Reduction. A Randomized Trial. Journal of the American Medical Association 293:43-53.

FOOD TODAY 04/2005