Promoters of high protein, low carbohydrate (HPLC) diets such as Robert Atkins (Atkins Diet) and Barry Sears (The Zone Diet) have induced a popular trend in weight loss nutrition. However, have these HPLC diets come at a cost to its followers? The purpose of this article is to address the claims and health concerns surrounding HPLC diets.

Claim 1: Weight loss is attributed to the composition of the diet (ie. carb vs. protein)

To achieve weight loss one must attain a negative energy balance; meaning that there are fewer calories consumed than expended (hypocaloric diet). This may occur in 3 ways. First, caloric expenditure may remain the same while calories consumed are restricted. Second, caloric expenditure (ie. exercise) can be increased while calories consumed (food intake) remains the same. Third, and most effective, combines the first two. Hence, a combination of lower food intake and exercise is employed, leading to a retained lean muscle mass while body fat is decreased.

Unfortunately, HPLC diets have received much popularity due to their hypolaric nature, thus, facilitating weight loss. As an example, Dr. Atkins recommends that dieters consume 1,400 calories/day during the first two weeks of his diet (Boucher, 1999), however, this represents only 60% of the recommended energy intake for a 18-yr old female weighing 125 lbs. A hypocaloric diet of any sort will yield weight loss, therefore, it is a negative energy balance, rather than diet composition, that is the cause.

Claim 2: Insulin promotes the storage of fat; therefore, by limiting carbs, dieters will decrease levels of insulin and body fat.

Insulin is an anabolic hormone released upon eating that allows the uptake and storage of carbohydrates and fat. High insulin levels are associated with obesity, yet it is inaccurate that promoters of HPLC diets have targeted insulin as the cause of obesity. Instead, it is obesity that causes high levels of insulin to accumulate by decreasing the liver's ability to clear insulin from the blood (Bergman, et al. 2001). Studies have even shown that decreased levels of insulin do not lead to greater weight or fat loss (Golay, Allaz et al. 1996; Golay, Eigenheer et al. 1996).

Claim 3: Weight loss is result of fat loss

Research suggests that water loss is responsible for the rapid weight loss associated with HPLC diets. Cham et al. (1981) found that subjects lost 4 kg on a low-carb diet but regained their weight within 24 hrs of resuming their regular diets. This can be explained by a decrease in water retention resulting from lower carbohydrate stores, since 1 molecule of glycogen (carbohydrate stored in muscle) holds 4 molecules of water.

Health Concerns

The American Medical Association (1977) has condemned the Atkins diet labeling it ?potentially hazardous?. HPLC diets in general have reported adverse health effects including:

?Calcium loss ? via increased urinary calcium excretion

?Undesirable lipoprotein levels ? higher LDL levels, and lower HDL levels predispose the dieter at risk of cardiovascular complications.

?Decreased immune function ? via lower levels of vitamins and minerals in diet.

In sum, promoters of HPLC diets have based their claims on research using obese and hyperinsulimenic subjects. This is misleading and inappropriate information for the general population to utilize and as such should be taken into consideration when embarking on a weight loss regime.