From a quantity of life standpoint, it’s far more important to be “fit” than to be a normal body weight. Stated otherwise, you can be fat and still be fit. “Fitness” includes our aerobic fitness (our VO2 max which is our ability to transport and utilize oxygen) and our muscle strength. The preponderance of research indicates that it is far more important to be fit regardless of how much we weigh.
To be clear, in large scale studies, as you can imagine, health risks increase as a person’s weight increases. Interestingly and somewhat surprisingly, mortality risks of overweight people changed “radically” if they were fit. Dr. Martin Gibala, professor and chair of the famed McMaster University Kinesiology department states, “It may seem shocking, but they discovered that overweight people who are fit have mortality risks similar to the risks of normal weight people. When we look at mortality rates in fat people who are fit, we see that the harmful effect of fat just disappears.”
Take home message: If you are carrying a few extra pounds (or more than a few) and you want to increase your lifespan, you don’t have to lose weight. It’s more important to start exercising to improve your muscle strength and aerobic fitness. Ideally, you should lose weight as well; but place your focus on getting fit. Being fat but fit is better than being normal weight (or even slim) but unfit.
PS, I think it’s a shame that we live in a society that focuses almost exclusively on our weight. Losing five pounds seems to be the main driver that underpins our exercise. This misplaced focus on weight loss has created multiple generations of people who are missing the real benefits of exercise.