With commentary by Osama Hamdy, MD, PhD, FACE, medical director of the Obesity Clinical Program the Joslin Diabetes Center in Boston and assistant professor of medicine at Harvard Medical School
People with type 2 diabetes who carried extra pounds had a survival advantage over those at a normal weight in a recent, controversial study from the University of Hull in the UK. Overweight study volunteers were 13 percent less likely to die over 10 ½ years than those at a normal weight, while risk for an early death was highest in the underweight and nearly equal for normal-weight and obese participants.
The researchers believe “normal weight diabetes” may be deadlier because it signals a greater genetic susceptibility to blood sugar and metabolic problems that could bring with it a higher risk for diabetes complications and other diseases.
However, while being overweight might have afforded participants in this study a longer life, carrying extra pounds didn’t mean better health. Volunteers who were overweight (a BMI of 25 to 29.9, such as weighing 159 to 185 pounds if you’re five-foot-six or obese, or a BMI of 30 or higher) were more likely to be hospitalized with cardiovascular problems than those at a normal weight. Extra weight boosted the odds for stroke and other cerebrovascular events by 4 to 26 percent; for heart failure by 35 to 122 percent; and for acute coronary syndrome by 34 to 62 percent compared to those at a normal weight (a BMI of 18.5 to 24.9 —equivalent to weighing about 115 to 154 pounds if you’re five-foot-six.)
Not everyone agrees with the conclusion from this large-scale long-term study. “BMI is the worst measure of obesity because it doesn’t take into account how much muscle versus fat a person has and where their fat is located,” says endocrinologist Osama Hamdy, MD, PhD, FACE, medical director of the Obesity Clinical Program the Joslin Diabetes Center in Boston and assistant professor of medicine at Harvard Medical School. “We know that central or visceral fat -- the kind inside your abdomen —raises risk for diabetes, heart disease and mortality regardless of BMI and this study did not account for that key variable. One in three normal-weight people have central obesity.”
“People with diabetes and prediabetes should not conclude that being overweight is better —though headlines about this study may make it sound that way. It isn’t true,” he says.
The study also didn’t factor in the effects of medications taken by the volunteers. “Metformin decreases risk for heart disease and cancer. Insulin and sulfonylureas increase risk for obesity. Cholesterol-lowering statins may reduce inflammation. All of these could affect the results,” notes Hamdy. The study did not include the cause of volunteers’ death, which also makes the data difficult to interpret, Hamdy adds.
“For people with type 2 diabetes or prediabetes, the best take-home message from this is that it’s important to pay attention to the real obesity paradox: Where your body fat is,” Hamdy says. “If your fat is in your hips and thighs — but not your torso — you may have a health advantage. But if your waistline measures 35 inches or more for women or 40 inches or more for men, take action. Keeping carbohydrate intake to 40 percent of total calories (or less) and getting aerobic and strength-training exercise regularly can reduce visceral fat quickly —by as much as 50 percent in just a couple of weeks.”
Citation: Costanzo et al: The Obesity Paradox in Type 2 Diabetes Mellitus: Relationship of
Body Mass Index to Prognosis. Ann Intern Med. 2015;162:610-618.
Costanzo, Figure 2, p. 6 of pd
Osama Hamdy, MD, PhD, FACE, Medical Director of the Obesity Clinical Program the Joslin Diabetes Center in Boston and Assistant Professor of Medicine at Harvard Medical School.