There are plenty of reasons why people want to lose weight. For some it’s purely aesthetic, but for others it’s a quality of life issue, or even a matter of life and death. At Peak Health Advocate, we often write about the increased risk for chronic diseases such as cardiovascular disease and diabetes that are associated with obesity. But is being thin really the issue? In other words, is it possible to be fat and fit, thereby reducing the health risks associated with being overweight?
Studies have shown that the risks of chronic disease are lower in obese men with moderate to high levels of aerobic fitness. 
But why is this?
One’s mind might jump to things like cholesterol levels or blood pressure, but research shows that these traditional risk factors may not fully explain why the risks of chronic disease are lower in men who are fat and in shape versus men who are overweight and out of shape. So UK researchers decided to take a look at traditional risk factors, along with some others, including insulin sensitivity and various liver markers.
They state, “The objective was to test the hypothesis that traditional and novel cardiometabolic risk factors would be significantly different in groups of men of different fatness and fitness.”
One-hundred forty-four nonsmoking white men aged 35 to 53 years were grouped according to waist girth and fitness (milliliters of oxygen per kilogram of fat-free mass):
- Sixty-two were slim and fit: waist girth ≤90 cm and maximal oxygen consumption [VO2max] above average in relation to age-specific norms, and did at least 60 minutes of vigorous-intensity activity per week in the last two years
- Twenty-four were slim and unfit: waist girth ≤90 cm and VO2max average or below, and did no regular moderate or vigorous-intensity activity in the last two years
- Thirty-nine were fat and fit: waist girth ≥100cm and VO2max above average, and did at least 60 minutes of vigorous-intensity activity per week in the last two years
- Nineteen were fat and unfit: waist girth ≥100cm and VO2max average or below, and did no regular moderate or vigorous-intensity activity in the last two years
The average age of the men was around 40 years, and about 80% of them were employed in managerial and professional occupations. Waist girth among the slim/fit and slim/unfit groups was not significantly different, and maximal oxygen consumption was not significantly different in men who were slim/fit and those who were fat/fit.
How They Measured Up
Researchers found that blood pressure was not significantly different in the slim/fit and slim/unfit groups but, as you can probably guess, was higher in men who were fat/fit and those who were fat/unfit.
As for HDL (good) cholesterol, it was not significantly different in the slim/fit, slim/unfit and fat/fit groups, but was lower in men who were fat/unfit. However, total cholesterol did not significantly differ among any of the groups. Yet triglyceride concentration was higher in men who were fat and unfit, and not significantly different among the other three groups.
Insulin resistance, which has been linked to cardiovascular disease and type 2 diabetes, was not significantly different in the slim/fit and slim/unfit groups, but was higher in the fat/fit group, and higher still in the fat/unfit group. The authors note that exercise has previously been shown to effect insulin sensitivity, and this may be because men who are fat and fit tend to store more excess fat in insulin-sensitive adipose tissue rather than the viscera or the liver when compared with men who are fat and unfit.
When it comes to inflammation, high-sensitivity C-reactive protein (CRP) is produced by the liver and the level rises when there is inflammation throughout the body. However, this measure was not significantly different in men who were slim/fit and those who were slim/unfit, but was higher in men who were fat/fit and those who were fat/unfit.
As for other liver tests, alanine aminotranferease (ALT) and aspartate aminotransferase (AST) were also measured. These are enzymes located in liver cells that leak out into the bloodstream when body tissue or an organ is damaged. ALT was not significantly different in the slim/fit and slim/unfit groups, but was higher in the fat/fit group, and higher still in the fat/unfit group. And while AST was not significantly different among the four groups, the ratio of AST to ALT was lower in the fat/fit group and lower still in the fat/unfit group. The AST:ALT ratio can help to differentiate between causes of liver damage. A higher ratio is more likely to be indicative of alcohol-related damage, while a lower one likely denotes a condition unrelated to alcohol, such as nonalcoholic fatty liver disease.
The researchers concluded, “Differences in HDL-C concentration, triglyceride concentration, ALT activity, and HOMA [insulin resistance] may explain why the risks of chronic disease are lower in men who are fat and fit than those who are fat and unfit. Our study of men who were fat, fit, and active is in keeping with the notion that physical activity and the pursuit of physical fitness reduce the risks associated with obesity.” (Editor’s note: The authors point out that, due to the makeup of this study, these results do not apply to women.)
Is Being Fit Good Enough?
It’s no secret that we are a country with a weight problem. According to the Centers for Disease Control and Prevention (CDC), two-thirds of U.S. adults are overweight or obese. And this puts them at a much higher risk for health problems including cardiovascular disease, diabetes and certain types of cancer.
But with this study showing that certain risk factors are mitigated in men who are fit and fat, does that mean it’s OK to be fat if you’re in shape?
Well some risk factors were shown to differ significantly in fat/fit men versus fat/unfit group, others such as blood pressure and the inflammation marker CRP, did not. Furthermore, while a high level of activity certainly seems as though it could help reduce your risk of disease if you’re overweight, there’s no denying that a maintaining a healthy body weight could decrease your chances even more.
The authors say, “The present study of cardiometabolic risk factors suggests that fitness reduces the risks associated with obesity; however, it is possible that fitness reduces all-cause mortality independent of cardiometabolic risk factors.”
Where does that leave us?
Well, if you’re overweight, you should definitely consider starting a fitness routine. Of course, be sure to check with your doctor first. And while increasing your activity level should have the effect of shedding extra pounds, it does seem that even if you never reach a weight that could be considered “slim,” you will still help your chances of staying healthy and avoiding chronic disease.
 Lee CD, Blair SN, Jackson AS. Cardiorespiratory fitness, body composition, and all-cause and cardiovascular disease mortality in men. Am J Clin Nutr 1999;69:373-80.
 Lee Dc, Sui X, Church TS, et al. Associations of cardiorespiratory fitness and obesity with risks of impaired fasting glucose and type 2 diabetes in men. Diabetes Care 2009;32:257-62.
 O’Donovana, Gary, et al. Fatness, fitness, and cardiometabolic risk factors in middle-aged white men. Metabolism 2011.