Can you have a healthy heart while overweight? A new study suggests that if you keep physically fit, you can.
"You can get fit," explains study leader Jennifer L. Kuk, who is an associate professor from the School of Kinesiology and Health Science at York University in Toronto, Canada, "without losing weight and have health benefits."
She and her team investigated the relationship between cardiorespiratory fitness and markers of cardiovascular health in individuals with mild to severe obesity.
Prof. Kuk explains that exercising for a total of 150 minutes per week — as recommended in national guidelines — is generally equivalent to losing less than half a pound in weight.
But this level of physical activity can bring considerable improvements in health for people with severe obesity.
"You really have to disconnect the body weight from the importance of fitness," she urges.
The researchers report their findings in a paper that was recently published in the journal BMC Obesity.
Overweight and obesity
The World Health Organization (WHO) define overweight and obesity as "abnormal or excessive fat accumulation that may impair health."
Body mass index (BMI) is a "crude measure" of obesity calculated by dividing a person's weight in kilograms by the square of their height in meters. Overweight is defined as having a BMI of 25 or higher, and obesity is defined as having a BMI of 30 or higher.
Using these measures, researchers have found that being overweight or obese likely puts people at higher risk for cardiovascular and other diseases, such as diabetes and cancer.
In the United States, more than two thirds of adults are overweight, including around a third who are obese.
As well as eating habits, there several other factors that play a role in overweight and obesity — such as genes, medical conditions, and being physically inactive.
Evidence suggests that more physical activity is needed to lose weight than is required to benefit health.
The new study is among the first to show that exercise may be even more important for people who are in the severely obese category — that is, those whose BMI exceeds 40.
Study assessed fitness and metabolic health
Prof. Kuk and colleagues analyzed data on 853 people who were attending a weight management clinic in Southern Ontario.
All participants underwent clinical exams, gave blood samples, and performed a "maximal treadmill test," during which cardiovascular and respiratory measures were recorded to assess fitness.
The team used three categories of obesity: mild (a BMI lower than or equal to 34.9), moderate (a BMI of 35–39.9), and severe (a BMI of 40 or higher).
The results showed that of those with mild obesity, 41 percent were considered fit, compared with 25 percent and 11 percent of those with moderate and severe obesity, respectively.
Participants considered fit were more likely to be younger (age 48, on average, compared with 51), be female, and have a lower BMI (36, on average, compared with 41).
Higher blood pressure, higher levels of triglycerides and glucose, and lower levels of high-density lipoprotein cholesterol were more prevalent in the moderate and severely obese participants.
'Important health benefits' for severely obese
The group whose members were classed as severely obese was the only group in which level of fitness seemed to make a significant difference to health measures.
For instance, the least fit 20 percent of the group were more likely to have higher levels of glucose and triglycerides as well as high blood pressure, whereas this was less of an issue in the fitter 80 percent of severely obese participants.
Also, the authors note that higher fitness was "associated with smaller waist circumferences, with differences between high and low fitness being larger in those with severe obesity than mild obesity."
It would seem, therefore, that if you are severely obese, avoiding being in the least fit 20 percent might be enough to make a significant difference to health.
The study authors suggest that their findings reveal the "potentially important health benefits of having a high fitness level, particularly for those with severe obesity."
This is in line with previous studies that have shown that you need to do a lot more exercise to lose weight than to improve health.
However, the researchers believe that their study is the first to support the idea that being fit might make more of a difference to health in people with severe obesity than losing weight.
"In my practice," says study co-author Dr. Sean Wharton, an adjunct professor at York University, "I see many patients who are looking for different results."
"There are some patients that want to significantly improve their health and others that are only looking for an aesthetic goal," he explains.
"When it comes to health, this study reinforces the notion that people don't need to lose weight to be healthy."
Dr. Sean Wharton