More muscle mass — and not just less body fat — is critical to lowering your risk for type 2 diabetes, a new UCLA study suggests.
Reporting in the September issue of the Journal of Clinical Endocrinology and Metabolism, researchers from the David Geffen School of Medicine at UCLA suggest there is a correlation between greater muscle mass, relative to body size, and a substantially decreased risk of developing the metabolic changes that lead to diabetes.
"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," said Dr. Preethi Srikanthan, an assistant professor of medicine in the division of endocrinology at UCLA. "This is a welcome message for many overweight patients who experience difficulty in achieving weight loss, as any effort to get moving and keep fit should be seen as laudable and contributing to metabolic change."
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.
For the current study, they again used NHAHES III data, this time on 13,644 adults who were not pregnant and had a BMI of at least 16.5, to see how this correlation applied to individuals representing the entire spectrum of muscle mass levels, rather than only those with sarcopenia. Specifically, they wanted to determine if there was a correlation between higher levels of muscle mass and lower levels of insulin resistance, a precursor to diabetes.
After controlling for age, race and ethnicity, gender, generalized obesity (high BMI), and central obesity (large waist), they found that for each 10 percent increase in the skeletal muscle index (SMI) — the ratio of muscle mass to total body weight — there was a corresponding 11 percent reduction in insulin resistance and a 12 percent reduction in pre–diabetes, a condition characterized by higher-than-normal levels of glucose in the blood.
"While we knew there was a relationship between metabolic disorders and very low muscle mass, we were surprised to find that this relationship was preserved across the range of muscle mass," Srikanthan said.
The study was cross-sectional rather than interventional, so the researchers cannot say for certain that increasing one's muscle mass will lower one's risk of developing insulin resistance or pre-diabetes. But given the strong associations they found, the research demonstrates the importance of monitoring relative muscle mass to get an idea of a person's risk for diabetes.
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.
Dr. Arun Karlamangla, a UCLA associate professor of medicine in the division of geriatrics, co-authored this study.
The National Institutes of Health funded this research.
The UCLA Division of Endocrinology, Diabetes and Hypertension, part of the department of medicine at the David Geffen School of Medicine at UCLA, provides consultative, diagnostic and therapeutic services for the full range of endocrine problems. The division has complete diagnostic and therapeutic capability, in association with members of the divisions of general surgery, neurosurgery and vascular surgery and the departments of ophthalmology and radiology.
The UCLA Division of Geriatrics within the department of medicine at the David Geffen School of Medicine at UCLA offers comprehensive outpatient and inpatient services at several convenient locations and works closely with other UCLA programs that strive to improve and maintain the quality of life of seniors. UCLA geriatricians are specialists in managing the overall health of people age 65 and older and treating medical disorders that frequently affect the elderly, including falls and immobility, urinary incontinence, memory loss and dementia, arthritis, high blood pressure, heart disease, osteoporosis, and diabetes. As a result of their specialized training, UCLA geriatricians can knowledgably consider and address a broad spectrum of health-related factors — including medical, psychological and social — when treating patients.