Mayo Clinic researchers report that healthy adults with slower metabolic rates are not at higher risk for weight gain.  The finding, which appears in the latest issue of American Journal of Clinical Nutrition, discounts a common myth and points to other far more important factors influencing weight gain.

“At the core of the issue of obesity is a persistent imbalance between energy intake and energy expenditure” says Michael D. Jensen, M.D., Mayo Clinic endocrinologist and senior author.  “One might expect that people with a lower basal metabolic rate would be more susceptible to future weight gain than those with high metabolic rates, but the data show no significant difference.”

Basal metabolic rate is a measure of the amount of energy expended by a body at rest. Many factors contribute to an individual’s baseline metabolic rate including age, sex, and body composition.

In this retrospective cohort study, 575 subjects were identified through electronic medical records. Then a subset of participants were grouped into a high metabolism group and a low metabolism group, which differed by 500 kilocalories/day. Further medical record investigation into the subgroup available for follow up showed that individuals in both groups had similar weight changes over time.

The researchers conclude that changes in other circumstances, such as the amount of physical activity, diet, or the effect of medications, contribute much more to the risk of weight gain than does basal metabolic rate.

Although these findings differ from previous studies, Dr. Jensen and colleagues are confident that the finding is accurate.

“We feel that those other studies may have come to different conclusions because of lesser sample size or studying very selected populations,” explains Dr. Jensen. “We have the advantage of being able to use Mayo’s electronic medical records to track the weight changes of  70 percent of our research volunteers for an average of 10 years.”

— John Jefferson, Ph.D.