Some people who are obese may have to work harder to lose weight due to metabolic differences, according to a recent study by researchers at the US's National Institutes of Health (NIH).

Published in the journal Diabetes, the study’s researchers at the Phoenix Epidemiology and Clinical Research branch of NIH studied 12 obese men and women using a whole-room indirect calorimeter – which allows energy expenditure to be calculated based on air samples. Researchers took baseline measurements of the participants’ energy expenditure in response to a day of fasting, followed by a six-week inpatient phase of 50 per cent calorie reduction.

After accounting for age, sex, race and baseline weight, the researchers found that the people who lost the least weight during the calorie-reduced period were those whose metabolism decreased the most during fasting. These people have what the researchers dubbed a “thrifty” metabolism – compared to a “spendthrift” metabolism in those who lost the most weight and whose metabolism decreased the least.

“When people who are obese decrease the amount of food they eat, metabolic responses vary greatly, with a “thrifty” metabolism possibly contributing to less weight lost,” said Susanna Votruba, PhD and study author. “While behavioural factors such as adherence to diet affect weight loss to an extent, our study suggests we should consider a larger picture that includes individual physiology.”

Researchers do not know whether the biological differences are innate or develop over time and more research is needed to determine whether individual responses to calorie reduction can be used to further prevent weight gain. The research provides further evidence that a more personalised approach is required when tackling individual weight loss – rather than employing one-size-fits-all weight loss programmes.