The size of an ageing man's belly and the bulk of his biceps provide a more accurate picture of his mortality risk than body mass index (BMI) alone, UK researchers have shown.
Among 4 107 men aged 60 to 79, those with a waist circumference less than 102 centimetres (40 inches) and above-average muscle mass in their upper arms were the least likely to die over a six-year period, Dr S. Goya Wannamethee of Royal Free and University College Medical School in London and colleagues found.
BMI, on the other hand, was only linked to mortality among very thin men, who were at increased risk of dying.
"In older men especially, we should not just be measuring weight but also their waist circumference and their muscle mass as measured by mid-arm muscle circumference," Wannamethee told Reuters Health.
Better than BMI
The researchers set out to determine whether belly fat and muscle mass might be more precise predictors of mortality by making several measurements of body composition in 4 107 men, 713 of whom died during the study's six-year follow-up period.
As people age they typically lose muscle mass and gain belly fat, Wannamethee and colleagues note in a report in the American Journal of Clinical Nutrition. These changes mean BMI may not provide an accurate picture of obesity and overweight in older people.
A man's risk of dying during the study dropped as his muscle mass rose, while both BMI and waist circumference alone showed little relationship to mortality.
Combining muscle mass and waist size provided the most accurate gauge of death risk. Men with waist circumferences greater than 102 cm and above-average muscle mass were 36 percent more likely to die than those with smaller waists and bigger-than-average muscles, while those with big bellies and small muscles were at 55 percent greater mortality risk.
Fitness is key
The findings underscore the importance of life-long fitness, Wannamethee noted. Men who have avoided obesity, particularly in the abdominal area, while keeping their muscle mass "are likely to enjoy longer, and almost certainly healthier lives," the researcher said.
"A combination of a prudent diet (low calorie, low saturated fat, and low alcohol) and regular moderate physical activity is required to achieve these ends," Wannamethee added.
"The key message is 'keep active' all the way to the end."
SOURCE: American Journal of Clinical Nutrition. – (Reuters Health)