According to a new study greater muscle mass may reduce the odds of developing diabetes. There have been studies that show having less body fat reduces diabetes risk and that exercise can help too, but the new study by UCLA scientists suggests a link between higher muscle mass and a lower risk of diabetes.
Preethi Srikanthan, an assistant professor of medicine in the division of endocrinology at UCLA's David Geffen School of Medicine said, “Our findings suggest that beyond focusing on losing weight to improve metabolic health, there may be a role for maintaining fitness and building muscle mass.”
For the study, published online Thursday and in the September issue of the Journal of Clinical Endocrinology and Metabolism, researchers analyzed data from 13,644 adults who participated in the National Health and Nutrition Examination Survey III (NHANES III) to determine whether there was a correlation between higher levels of muscle mass and lower levels of insulin resistance, a precursor to diabetes. They controlled for age, race and other factors.
Results showed that for each 10% increase in the skeletal muscle index — the ratio of muscle mass to total body weight — there was a corresponding 11% reduction in insulin resistance and a 12% decrease in pre-diabetes.
According to the American Diabetes Association, 79 million people in the USA have pre-diabetes, which means their blood glucose levels are higher than normal but not in the diabetes range yet.
Daniel Rubin, an assistant professor of medicine in the division of Endocrinology at Temple University School of Medicine said this is consistent with what is already known about muscle and fat — that they do affect metabolism. He said, “Extra fat has bad effects, but more muscle has good effects. These data are also consistent with data we see on exercise, that it helps decrease diabetes risk, and that a lack of exercise and weight gain increase risk.”
Srikanthan points out that the study was not an intervention, it was observational. It's difficult to know when looking at a correlational study like this one whether it's just a correlation or an effect, says Duke endocrinologist Susan Spratt. “Are there other healthy behaviors that tag along with high muscle mass that reduce the risk of diabetes? We don't know from this study that if you increase muscle mass you will decrease insulin resistance, but we can infer that might be the case,” Spratt said. Srikanthan said, “We should consider monitoring improvements in muscle mass in addition to changes in fat.”
In 2009, the UCLA researchers published a study suggesting that the ratio of waist size to hip size - an indirect measure of abdominal fat, relative to gluteal musculature - is a better predictor of premature death in older adults than either body mass index (BMI) or waist circumference. They then examined a condition called sarcopenic obesity, in which there is a low level of total body muscle mass (sarcopenia) combined with a high BMI (obesity), theorizing that the presence of this condition would correlate with higher insulin resistance and diabetes risk. The following year, they tested this hypothesis by examining data from the National Health and Nutrition Examination Survey III (NHANES III); the data were culled from health information collected between 1988 and 1994 on 17,000 people aged 20 and older - a large number of people of various ages. They found that sarcopenia was associated with increased insulin resistance in both non-obese and obese individuals, and also with higher levels of blood glucose in obese individuals.
The researchers now want to perform a similar analysis in a large data set containing a better measure of both muscle mass and body fat, Srikanthan said. “Further, we have an imaging technique to look at the quality of muscle in obese patients and diabetics, and we would be interested in seeing how this changes over time and with different interventions,” she said
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