Posted on 07/15/2022 10:13:58 AM PDT by nickcarraway
Researchers say they have debunked the urban myth that healthy underweight people “eat whatever they want and burn it off with exercise”.
A study of healthy Chinese adults considered underweight, according to the widely used Body Mass Index (BMI), found they not only do not eat as much food as people with a “normal” BMI, they are also less physically active.
More from AsiaOne Read the condensed version of this story, and other top stories with NewsLite. “Our data suggests they eat about 12 per cent less than adults with a normal BMI,” the team of scientists wrote in an article published by the peer-reviewed journal Cell Metabolism on Thursday.
“We can reject the hypothesis that healthy underweight adults derive their leanness from high levels of physical activity.”
The team, drawn from institutes including the Chinese Academy of Sciences, Beijing Technology and Business University and the University of Aberdeen in Britain, said the study’s “healthy underweight” participants were 23 per cent less active than the group with a normal BMI.
They also had higher-than-expected resting metabolic rates with an elevated resting energy expenditure and thyroid activity, the scientists said.
The researchers say their findings contradict the hypothesis that healthy underweight adults derive their leanness from high levels of physical activity. PHOTO: John Speakman The researchers said very little is known about the lifestyle and physiology, genetics, and how metabolism correlates with leanness among people classified by the BMI as healthy, yet lean.
The team recruited 173 people in Beijing aged between 20 and 40 with a normal BMI and 150 others defined by the index as “healthy underweight” for the study in 2017 and 2018.
The underweight group had a BMI below 18.5 with no eating disorders, HIV infection or weight loss related to illness in the previous six months. The group was dominated by women, at 83 per cent compared to 47 per cent in the group with a normal BMI.
The researchers said it was unclear whether women are over-represented in the lean and healthy population, or if they are more likely to volunteer.
The participants wore a motion detector on their waists to measure physical activity, while their daily energy expenditure was measured by an isotope-based technique using doubly-labelled water which predicts food intake.
Researchers John Speakman (left) and Zhang Xueying with a study participant. PHOTO: John Speakman Doubly labelled water looks and tastes like ordinary water but some of the hydrogen and oxygen has been replaced with isotopes of these elements which can be traced in urine samples.
The technique allows researchers to measure the body’s carbon dioxide production to assess energy expenditure based on the difference between the washout rates of hydrogen and oxygen.
In this study, the doubly-labelled water and urine samples were prepared and analysed by the University of Aberdeen.
The study’s lead author Hu Sumei, a lecturer at the Beijing Technology and Business University’s school of food and health, said the BMI – while a handy tool – should be seen as just one health indicator, alongside other factors such as body composition and metabolic rate.
“The takeaway is that eating less in quantity and having less fat body mass could be more important than being active in weight management and maintaining health for healthy underweight people,” she said.
Hu said the team will expand its research with a similar study in Shenzhen, southern China. They also want to look at the genetic differences between healthy underweight people and their counterparts with a normal BMI.
Stating the obvious for most thin people.
The money quote
They also had higher-than-expected resting metabolic rates with an elevated resting energy expenditure and thyroid activity, the scientists said.
You can’t exercise enough to eat all you want.
Well, one needs calories to exercise or perform physical work; so, no calories, no exercise or work. No calories means starvation and ultimate death.
A properly made taco is a good food that like a cheese burger contains all the food groups
Lose wait by eating less and exercising....hell anybody can do it that way!!!! My way is to eat lots of carbs and lay around all day!!!!
Only if fries are included!!!
I think urban people tend to be thinner because they are forced to walk more - a lot more. It maybe 2-3 blocks to the bus stop, and even farther to a subway station. And when you get off the subway, it may still be several more blocks to where you want to go. That’s my experience in big cities.
In the suburbs or county, we tend to DRIVE up to the place we want to go and then just walk right in from the parking lot.
Exercise burns relatively few calories. A hamburger bun alone without anything in it will fuel you for a mile walk.
Most calories are burned for basal metabolism or stored as fat.
Claiming that healthy underfed underweight people are necessarily less physically active is as non-nonsensical as holding that all healthy underweight people eat whatever they want and burn it off with exercise, which false premise is what the researchers can only imagine they are refuting.
“Most calories are burned for basal metabolism or stored as fat.”
Yes, but one needs calories to store. Absent caloric intake, ketosis will develop and eventually the body will begin feeding on itself (i.e., muscle cells and fat cells), which is autophagy; until, eventually, the organism dies. A very nasty end.
I had a Chinese lady that worked in the shop I used to go to in Shanghai ask me Do you know why Chinese women are better than American women? Because we work harder and eat less!”
Haven’t seen that pic in years. Truly a classic.
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