We’ve been told over and over that a healthy low Body Mass Index (BMI) is the result of eating less, eating healthier, and embracing a more active lifestyle. But researchers have discovered that folks with the lowest healthy BMIs are not necessarily more active…
Slightly-underweight-but-healthy people may prove that low
BMI is more important than exercise to cardio health…
What they did
An abstract of the study report explains: “The investigators recruited 173 people with a normal BMI (range 21.5 to 25) and 150 who they classified as ‘healthy underweight’ (with a BMI below 18.5).” Their food intake and physical activity were measured using the latest, most accurate laboratory methods.
What they found
“Compared with a control group that had normal BMIs, the healthy underweight individuals consumed 12 percent less food. They were also considerably less active, by 23 percent. At the same time, these individuals had higher resting metabolic rates, including an elevated resting energy expenditure and elevated thyroid activity.”
The takeaway
“We expected to find that these people [were] really active and to have high activity metabolic rates matched by high food intakes,” observes report corresponding author Dr. John Speakman of the Shenzhen Institutes of Advanced Technology in China and the University of Aberdeen in the UK. “It turns out that something rather different is going on. They had lower food intakes and lower activity, as well as surprisingly higher-than-expected resting metabolic rates linked to elevated levels of their thyroid hormones.”
Very low-BMI folks may have genetic changes that trigger their condition. The researchers have determined that mice with a certain genetic modification react the same way.
“Although these very lean people had low levels of activity, their markers of heart health, including cholesterol and blood pressure, were very good,” says report first author Dr. Sumei Hu of Beijing Technology and Business University. “This suggests that low body fat may trump physical activity when it comes to downstream consequences.”
My take
Seems reasonable that genetic differences or modifications could bring about the effects described by Speakman and Hu. Sounds as though follow-on research could lead to a new approach for treating obesity. The genetic link also, logically, dovetails with findings that a certain gene is responsible for some folks being able to eat whatever they want to and not get fat.
But I also think that most of us would be better off following the conventional advice: to eat healthier, eat less and espouse a more active lifestyle. That would help here and now – much preferable to waiting for a miracle treatment in some uncertain, distant future…
~ Maggie J.