Because a normal range of insulin response has yet to be established, it's too early to get the kind of blood test used in the study. (For the purposes of his research, Ludwig simply drew a line through the middle of his volunteers' scores to separate high and low responders.) But a mirror might help you tell if the low-glycemic diet is right for you. "High-insulin secretors tend to be apples, with more fat around the middle," maintains Ludwig. "Low-insulin secretors tend to be pears."
But the diet may be worth a try for anyone who's losing a battle with the bathroom scale. "Most overweight people have insulin issues," says Walter Willett, MD, chair of the department of nutrition at the Harvard School of Public Health. He, too, believes that for many people a low-glycemic diet is a more effective way to lose weight than limiting fat. The Mediterranean-based eating plan he espouses in his book Eat, Drink, and Be Healthy happens to be low glycemic. "The majority of people are metabolically better off with a diet higher in healthy fats," Willett says. "We have a built-in craving for fat, and low-fat diets are generally not satisfying, which is why they often don't work for the majority of people."
In the next few years, we may enter a new era of weight management when diets can be customized based on biological factors. But there's no reason you should wait to try a low-glycemic plan; it's essentially healthy, thanks to the focus on eating good fats and fiber and fewer simple sugars. "Obviously, hunger is one of the key downfalls of dieting," says Ludwig. "If weight loss can be achieved by eating till you're satisfied, that's an attractive approach for anyone."