Overweight doesn’t have to mean unhealthy. New research shows that physical exercise can negate, even overcome, the negative health impact of weight — even for the severely obese, even if you don’t lose weight.

Image credits Michal Jarmoluk.

A new study led by Jennifer Kuk, associate professor at York University, found that individuals with severe obesity who partake in exercise and are fit have a health profile comparable to those who weigh significantly less. The research looked at the benefits of cardiorespiratory fitness for heart and circulatory system health in populations with mild to severe obesity.

The findings suggest that even individuals with a BMI over 40 (which is considered to be severely obese) can be fit and healthy, provided they engage in exercise.

“Obesity is only related with worse health in individuals who were unfit,” says Kuk. “We know that once you get beyond a BMI of 40, the risk of cardiovascular conditions increases exponentially so this study shows that having a high fitness level is still beneficial and it really reinforces the importance of fitness.”

She says that following physical activity guidelines, which recommend 150 minutes of exercise per week, generally only translates to half a pound of weight loss. However, despite the modest reduction in weight, this amount of exercise did translate to significant improvements in the health of those with severe obesity.

The team worked with 853 Canadian patients from the Wharton Medical weight management clinics in Southern Ontario. The participants underwent a clinical exam that included measurements of fasting blood sugar levels and maximal treadmill stress tests, which the team used as a baseline. The researchers compared these initial measurements to later ones taken during the weight management program to establish the effect of exercise on their overall health.

It took surprisingly little exercise (in the form of cardiovascular fitness) for the team to find meaningful improvements in the health of participants. Specifically, all those who avoided lagging behind in the lowest 20% fitness bracket (4 in 5 participants) were in good enough physical shape to see health improvements, the authors report.

“You really have to disconnect the body weight from the importance of fitness,” Kuk adds. “You can get fit without losing weight and have health benefits.”

Some 41% of the mildly obese participants had high fitness levels by the end of the programme, while 25% and 11% of participants with moderate and severe obesity respectively, had high fitness levels. Participants with severe obesity were more likely to have high blood pressure, as well as high glucose and triglyceride levels if they were in the lowest 20% fitness level bracket. However, they were not more likely to have these issues if they were in the top 80% fitness level bracket.

All in all, the results show that physical activity is much more important for the general health of people with severe obesity but, despite what that glam magazine might tell you, you don’t have to lose weight to be healthy — all you need to do is exercise and stay fit. And you can take heart in the fact that previous research has shown that you need much less physical activity to gain health benefits than to shed pounds.

So if all you want to do is to stay healthy, weight is a far less important factor than exercise. If your waistline is the bottom line, you’ll have to put in a few extra hours at the gym.