According to the ADA, low-carb diets and others like it trigger short-term weight loss through a process called ketosis. This process kicks in when your body is in short supply of carbohydrates, a prime source of energy for the entire body, but especially for the brain, which operates exclusively on carbohydrates.
During ketosis, your carbohydrate-depleted body grabs other sources, including ketones from stored fat or protein, to satisfy daily energy needs. This leads to ketoacidosis, a state similar to that seen with type 1 diabetes. This type of diet can have a negative long-term impact on health.
"Next time you talk to someone on one of these diets, pay attention to their mental state, how alert they seem," says Holden. "The lack of carbohydrates tends to make them seem a bit fuzzy mentally because the brain is not getting enough fuel. Is that any way to diet?"
New Research Supports It
But a study in the July 2002 issue of the American Journal of Medicine showed that the most famous of low-carb diets -- the Atkins diet -- does work.
Study participants lost an average of 20 pounds while on the Atkins diet for six months, but they were not followed longer to see if they kept the weight off. Most people also had improved cholesterol levels at the end of the study, even though the eating plan permits unlimited quantities of cholesterol-rich foods such as eggs and meat.
The study was funded by a grant from the Robert Atkins Center for Complementary Medicine. Duke researcher Eric Westman, MD, says he became interested in studying the Atkins diet after several of his patients lost large amounts of weight on it.
But though researchers were impressed by the weight loss, they say more study is needed to pronounce the carbohydrate-restricting diet safe.
Here's how the American Heart Association says to take weight off -- and keep it off.
- Be active -- try walking 30 minutes a day most days of the week.
- To lose weight, most women should eat 1,200-1,500 calories per day.
- To lose weight, most men should eat 1,500-1,800 calories a day.
- A loss of one to two pounds per week is considered a healthy weight loss.
- People who lose weight gradually are more likely to keep the weight off.
- Eat no more than 30% of your total calories from fat.
- Include at least five servings of fruit and vegetables in your diet each day.
- Examine your eating habits -- keep a written journal of what and when you eat.
- Weigh yourself only once a week.
- Eat breakfast to curb binge eating.
"There are still a lot of things we don't know about food and nutrition," says Holden. "Nutrition is a relatively young science, but we do know that you can trick the body's mechanisms in the short run. In the long run, however, those short cuts catch up with you in the form of weight gain."