News

It's news that contradicts current healthy-eating advice -- a diet heavy on meat and cheese and void of whole grains and fruit can help you lose weight and may even help reduce heart-disease risk, according a study released today.

The surprising findings suggest that dieters who lost faith in the low-carbohydrate regime out of concern for their health, might want to reconsider the weight-loss plan.

Based on a comparison of four weight-loss diets, the low-carbohydrate diet was deemed most effective at helping overweight women shed pounds.

The most popular low-carb regime, developed by Dr. Robert Atkins, was first published in 1972 as Dr. Atkins' Diet Revolution. The diet's appeal skyrocketed in the 1990s and it remained popular until 2004.

Followers drastically cut carbohydrates by shunning breads, cereals, pasta, rice, fruit and milk and emphasizing protein-rich foods such as cheese, meat, poultry and fish. But cutting carbs and eating more protein and fat concerned many doctors and nutritionists, who feared it could lead to high cholesterol and blood pressure, risk factors for heart disease.

The A to Z Weight Loss Study, published today in the Journal of the American Medical Association, demonstrated the low-carb diet was not only the most successful at promoting weight loss, it also did not raise blood pressure or significantly boost cholesterol. Following the diet was actually associated with greater improvements in blood triglycerides, HDL (good) cholesterol and blood pressure.

In the year-long study, researchers assigned 311 overweight and non-diabetic women, aged 25 to 50, to one of four weight-loss diets representing a spectrum of low- to high-carbohydrate intake (see chart).

At the lowest end of carbohydrate intake was the Atkins diet. Women in the Atkins group aimed to consume no more than 20 grams of carbohydrate a day (roughly 18 per cent of calories) for the first two to three months and 50 grams a day or less for the subsequent "ongoing weight-loss phase."

The second group followed the moderate-carbohydrate Zone diet; a third group followed the high-carbohydrate LEARN diet; the remaining women were assigned to the very-high-carbohydrate Ornish diet.

Study participants worked with a dietitian one hour a week for eight weeks to read their assigned diet books cover to cover so that they thoroughly understood them. They were also given recommendations for exercise, nutritional supplements and behavioural strategies consistent with those presented in each diet book. Then, after eight weeks, they were left on their own for an additional 10 months to follow their diets.

At 12 months, weight loss in the Atkins group was significantly greater than with the other diets. Average weight loss was 4.7 kilograms (10.3 pounds) for Atkins, 1.6 kilograms (3.5 pounds) for Zone, 2.6 kilograms (5.7 pounds) for LEARN, and 2.2 kilograms (4.8 pounds) for Ornish.

An evaluation of each diet's impact on cardiovascular risk factors revealed that changes to HDL (good) cholesterol and blood triglyceride numbers favoured the Atkins diet at all times in the study. The decrease in blood pressure was also the largest in the Atkins group.

Other recent studies comparing weight-loss diets also reported that triglycerides, HDL cholesterol and blood pressure were not significantly different or were more favourable among low-carbohydrate-diet followers.

The lowest carbohydrate diet did not outperform the others when it came to reducing LDL (bad) cholesterol. After two months, the LEARN and Ornish diets lowered LDL cholesterol by 7.3 and 10 per cent respectively. By the end of the study, however, the LDL cholesterol-lowering effect of these diets diminished (possibly because followers became less compliant with their diets).

In the Atkins group, LDL cholesterol actually increased by 2 per cent after following the diet for two months. A higher LDL cholesterol might seem to be a negative effect of a high-protein, high-fat diet, but researchers say this might not be the case.

The triglyceride-lowering effect of a low-carbohydrate diet -- in this case a 30-per-cent drop -- leads to an increase in the size of LDL cholesterol particles. Research has shown that small, dense LDL particles are more often associated with hardening of the arteries than large, "fluffy" LDL particles.

How a low-carbohydrate diet causes weight loss is still unclear. It has been argued that weight loss is the result of consuming fewer calories by eliminating entire food groups. However, during the study, total daily caloric intake was not different among the diets. At two months, women in all diet groups were consuming roughly 1,430 calories a day.

The researchers speculate that increased water intake among Atkins followers may have played a role in weight loss. The higher protein content of the diet also may have helped dieters feel full longer after eating, although satiety was not assessed.

Its success may also hinge on its simplicity: Drastically reduce carbs, especially refined carbohydrates such as white bread, white rice, table sugar, sugary drinks and sweets.

This study adds to mounting evidence that a low-carbohydrate diet is an effective way to lose weight and does not increase the risk of heart disease -- at least for the short term. It remains unseen whether the weight-loss and risk-factor benefits of a low-carbohydrate diet can be sustained longer than one year.

It can be difficult to stick to a monotonous diet for a long period of time. In this study, Atkins followers actually gained some weight back between six and 12 months, suggesting the diet might be difficult to sustain long term. Adherence to each of the four diets waned over time, but more so for the Atkins and Ornish diets.

While the Atkins diet can help you lose excess weight, how successful you'll be at maintaining a lower weight depends on factors beyond the amount of carbohydrate, protein or fat in a diet.

Permanent weight loss requires strategies for long-term structured guidance and support, and emphasis on expending more calories through exercise. That's something to keep in mind if you decide to follow the Atkins diet, or any other weight-loss diet.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Visit her website at lesliebeck.com.

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Diets head-to-head

In the year-long study, researchers assigned 311 overweight and non-diabetic women, aged 25 to 50, to one of four weight-loss diets representing a spectrum of low- to high-carbohydrate intake.

ATKINS

What is it: Followers drastically cut carbohydrates by shunning breads, cereals, pasta, rice, fruit and milk and emphasizing protein-rich foods such as cheese, meat, poultry and fish.

Author: Dr. Robert Atkins first published his diet approach in 1972 in a book called Dr. Atkins' Diet Revolution.

Weight loss in 12 months: Average weight loss was 4.7 kilograms (10.3 pounds).

LDL results: Low-density lipoprotein, or so-called bad cholesterol, increased by 0.8 per cent after following the Atkins diet for 12 months.

*****ZONE

What is it: A moderate-carbohydrate plan that emphasizes meals and snacks containing a ratio of 40 per cent carbohydrate, 30 per cent protein and 30 per cent fat.

Author: Dr. Barry Sears popularized the diet plan in a series of books. The "Zone" is Dr. Sears's term for proper hormone balance -- when insulin levels are neither too high nor too low.

Weight loss in 12 months: 1.6 kilograms (3.5 pounds).

LDL results: After 12 months, the Zone diet had no impact on LDL cholesterol, neither lowering it nor raising it.

*****LEARN

What is it: A high-carbohydrate plan that includes 55 to 60 per cent of daily calories from carbohydrates and less than 10 per cent of calories from saturated fat.

Author: The LEARN diet is part of a comprehensive lifestyle program developed by Dr. Kelly Brownell, a psychologist and director of the Yale Center for Eating and Weight Disorders.

Average weight loss in 12 months: 2.6 kilograms (5.7 pounds).

LDL results: After 12 months, the LEARN diet raised LDL cholesterol by 0.6 per cent.

*****ORNISH

What is it: A very-high-carbohydrate diet with no more than 10 per cent of calories from fat. This vegetarian diet emphasizes low-fat, high-fibre foods such as legumes and whole grains.

Author: Developed by Dr. Dean Ornish in his book A Program for Reversing Heart Disease.

Weight loss in 12 months: 2.2 kilograms (4.8 pounds).

LDL results: After 12 months, the Ornish diet lowered LDL cholesterol by 3.8 per cent.