Diets and Obesity Surge Among Young and Adult Patients

October 4, 2005

Americans are caught in a twin epidemic. On one side is a rising tide of obesity, fueled by changes in eating habits, diet, and exercise. On the other side is a tide of diet plans, fueled by our desire for a magic bullet to cure the problem with minimal effort.

Americans are caught in a twin epidemic. On one side is a rising tide of obesity, fueled by changes in eating habits, diet, and exercise. On the other side is a tide of diet plans, fueled by our desire for a magic bullet to cure the problem with minimal effort.

"For my entire career, I have been trying to help people lose weight," Corey Evans, M.D., director of medical education at St. Anthony's Hospital in St. Petersburg, FL told the American Academy of Family Physicians Scientific Assembly. "It has been a discouraging process."

"We are having a tidal wave of obesity. Right behind it is a tidal wave of diabetes that is swamping primary care physicians."

The basic problem is simple enough, Dr. Evans said. People consume more calories than they burn and the excess appears as fat. The solution, reverse the equation to burn more calories than they consume, is complicated by The Great Diet Debate: What is better, low fat or low carb?

Both types of diets work in the short term, Dr. Evans said. But the key to successful weight loss isn't losing pounds, it is keeping them off. For the answer, he suggested turning to the evidence.

The National Weight Loss Registry includes about 5,000 Americans who have lost at least 30 pounds and kept them off for at least one year. The average weight loss was 66 pounds and the average duration of loss was 5 years.

Most of the successful losers used a combination of low fat, low caloric density diet plus exercise. The average fat content was 23%, although one third of enrollees consumed less than 20% fat. The current American Heart Association recommendation, Dr. Kent noted, allows up to 30% fat.

Fewer than 10% of registrants used diet alone to lose weight. Less than 1% used exercise alone. "It is the combination approach that works for most people," Dr. Kent noted.

Low-carb diets are effective at producing weight loss in the short term, three to six months, but are no more effective for weight loss than low fat diets at the one-year mark.

An analysis of eight diets by the University of Kentucky and an associated VA Medical Center in 2000 found that low carb-diets are high in saturated fats and cholesterol. Long-term use would increase serum cholesterol and risk for coronary artery disease. Diets low in fat but higher in carbs and fiber show the greatest reduction in serum cholesterol and CAD risk.

The projections match the results of a 2003 study of ketogenic diets in children with seizure disorders. After six months, the cohort of 141 children showed significant increased in total cholesterol, LDL, VLDL, and triglycerides; significant decreases in HDL; and a jump in atherogenic total apoB.

"Low-fat diets do not work long term because they are not low enough in fat," Dr. Kent said. "And there are serious safety questions when low-carb diets are followed long term."

The best long term solution, he said, is at least 30 minutes of exercise five to six days a week and a low fat, high complex carb diet with lots of vegetables and fruit. Patients should be advised to eat until they are full, but to eat foods with a low caloric density. As long as the average caloric density of all foods consumed is less than 400 calories per pound, patients can expect to lose weight and keep it off.