Being fit is an essential part to staying healthy, but is it enough to avoid diabetes and heart disease?

Credit: Tooga/Getty Images

Tooga/Getty Images YES: In fact, its a worthy goal.
Steven Blair, PED, professor of exercise science, epidemiology and biostatistics at the University of South Carolina

Its better than being thin and unfit.
Overweight people who exercise just 150 minutes a week have half the risk of mortality of normal-weight people who dont exercise at all, according to research I conducted. Thats not true once you move from overweight (meaning a body mass index, or BMI, of 25 to 29.9) to obese (a BMI of 30 or more). But being fit and a little fat seems to be fine.

Weight alone doesnt raise disease risk—lack of fitness does.
In one study, half of overweight adults and one-third of obese people who were active had normal blood pressure, cholesterol, triglycerides, and blood sugar, putting them at normal risk for heart disease and diabetes, which are both supposedly caused by weight.

Getting fit is more realistic than getting slim.
For most people, diets dont work in the long term. We ought to be thinking about different strategies. Its far easier for a fat person to get fit than thin.

NO: Exercise alone isnt enough.
Frank Hu, MD, PhD, professor of nutrition and epidemiology at Harvard School of Public Health

You cant be obese and fit.
Unless youre in that tiny fraction of the population—like pro athletes or the very muscular—whose muscle mass explains their high BMI. For most people with a BMI of 30 or more, their fitness is reduced by their weight, and their risk of conditions like diabetes and heart disease goes up.

Exercise doesnt erase all the risks of being heavy.
Yes, physical activity is important, but so is watching what you eat. Most studies show that both diet and exercise are important for diabetes prevention, for instance. And a study in the journal Obesity suggests that people with the highest BMIs have unhealthy eating habits.

Playing down the problem of excess weight is dangerous.
If youre heavy, you can cut your mortality risk by eating well and exercising—but research suggests that even active obese people are at 91% greater risk of dying than active people of normal weight.

Our advice:
The health equation is more complicated than fat equals bad and slim equals good. It is clear, though, that avoiding obesity by eating a healthful diet and exercising helps both prevent disease and lengthen your life. So make sure youre as fit as you can be: Aim for a well-balanced diet of whole foods eaten in moderation and a workout regimen of at least 30 minutes of cardio five days a week, plus twice-weekly strength-training sessions.