First things first: Weight is relative. A six-foot-tall man and a five-foot-tall woman may each weigh 200 pounds, but they're going to look (and feel) a lot different carrying it. So to look more objectively at weight and health, health experts devised a calculation of weight in relation to height called body mass index, or BMI.
The trouble with BMI is it doesn’t take into account what makes up your weight.
Very muscular athletes may fall into the overweight or obese category, for example, even if they have very little body fat. And people with very little muscle mass—so called “skinny obese” people—may have a normal weight-to-height ratio but also have high blood pressure, high cholesterol, and increased risk of chronic diseases.
Further complicating the issue of weight and health, it is possible to carry around extra weight and still be "metabolically healthy," meaning that you have normal blood pressure, cholesterol, and blood glucose levels. But often, people who are overweight aren't eating healthy foods or exercising regularly, says Dr. Michael Emery, MD, Sports Council Co-Chair for the American College of Cardiology. But that doesn’t mean thin people are off the hook. "Our normal weight patients with these same habits are also at risk, but it's just not as obvious," Emery says.
Some research has also suggested that being slightly overweight may be healthier than being slightly underweight, although that's a pretty complicated topic in itself.
So the short answer is no. Weight alone is not a good indicator of health; it must be combined with other measures to truly get a feel for your wellbeing. Body-fat percentage, measured by special scales or by devices in clinics and doctor's offices, is a helpful health indicator; the more fat tissue you have, the harder it becomes for your body to perform basic functions like convert glucose to fuel and pump blood through your veins.
Visceral fat, which collects around the abdomen, seems to be especially hard on the body's organ systems. "If we really wanted to look at someone's overall health, we'd want to know their waist circumference and their waist-to-hip ratio," says Dr. Y. Claire Wang, co-director of Columbia University’s Obesity Prevention Initiative. "We know waist-to-hip ratio indicates higher risk for diseases like diabetes."
Emery councils his patients about weight, and he takes note if they seem heavier or thinner than they should be. But if he knows a patient is eating well and getting regular exercise, he's not always concerned about a bigger-than-average belly.
"It would depend on things like their cholesterol profile, their insulin sensitivity, and their family history," he says. "And it would depend on their performance goals, as well: If an athlete wants to get faster or increase endurance, he may need to lose weight to improve his training."
Bottom line: Extra weight is often a side effect of unhealthy habits, and a warning sign of potential complications—if not now, then later down the road. But a few pounds probably won't doom you to a life of chronic disease. How you feel, how you eat, and how you move will always be more important than the number on the scale.