Obesity has little to do with inactivity, according to researchers
A new study concludes that what we eat plays a far greater role.
For cardiovascular diseases, cancer, type 2 diabetes, high blood pressure, falls and fractures, mental health, and much more, physical activity is extremely important. But for weight loss, it's less important, according to researchers.(Photo: Shutterstock / NTB)
For decades, these have been the main explanations for rising obesity rates in wealthy countries.
An international group of researchers has now tested these two explanations against each other.
Comparing different lifestyles
The researchers analysed data from 4,200 adults from 34 population groups across six continents.
Annonse
These people live very different lives:
"Whether people live as hunter-gatherers or in modern industrial societies, their total energy expenditure is about the same," says Ulf Ekelund.(Photo: Norwegian School of Sport Sciences)
Hunter-gatherers in low-income countries like Tanzania. Small-scale farmers in Bolivia. Livestock herders in Siberia. City dwellers in high-income countries like Norway and Sweden.
All participants had their daily energy expenditure, body mass index (BMI), and body fat percentage measured.
Almost no difference in energy expenditure
As expected, participants in wealthy countries had higher BMI and body fat percentage.
What surprised the researchers was that, after adjusting for body size, total energy expenditure was roughly the same across lifestyles.
"The study shows that whether people live as hunter-gatherers or in modern industrial societies, their total energy expenditure is about the same," says Ulf Ekelund.
He is a professor at the Norwegian School of Sport Sciences and contributed to the study.
When researchers equip participants with sensors like pedometers and accelerometers, they find that hunter-gatherers are far more active than city dwellers in industrialised societies.
The small difference in total energy expenditure, however, may be due to the fact that people in industrialised nations tend to be taller and have greater overall body mass than those in poorer countries.
The researchers believe this is likely connected to better access to nutritious food.
Physical activity sill matters
"Does this mean that physical activity is less important than we previously thought?"
"At the population level, when it comes to obesity, that seems to be the case," says Ekelund. "But for individuals, physical activity can absolutely have an impact, both for preventing weight gain and for health in general."
He points out that physical activity remains essential for cardiovascular diseases, cancer, type 2 diabetes, high blood pressure, falls and fractures, mental health, and much more.
Diet is the key to weight loss
The results confirm what many studies have shown before – that it is very difficult to lose weight simply by being more physically active, says Ekelund.
"This is also supported by several randomised studies. They show that energy intake may explain 80 per cent of weight loss, while physical activity alone plays a much smaller role," he says.
"To put it simply: You can eat a slice of cake worth 500 calories in one minute, but it takes about an hour of brisk walking or running to burn those same calories," he adds.
Often overestimated
Marte Isaksen Aukan is a researcher at NTNU with a background in nutrition and clinical health sciences. She has read the study but did not take part in it.
"We do indeed burn more energy when we're active than when we're sitting still, but the difference is often overestimated. The body quickly adapts and becomes more efficient," says Aukan.
She explains that it therefore takes a significant amount of physical activity to compensate for an unhealthy, high-energy diet.
It's not about willpower
"There are many causes of obesity, and weight gain from increased energy intake stems from a complex interaction between biology, environment, and psychology," says Marthe Isaksen Aukan.(Photo: Private)
Aukan emphasises the importance of recognising that obesity has many causes and that weight gain from increased energy intake results from a complex interplay of biological, environmental, and psychological factors.
"It's not about willpower. Stress, hormones, the brain's reward system, inattention, socioeconomic status, and our surroundings all play a role," she says.
In today's society, it's hard to avoid tempting foods, Aukan believes.
"Such foods are often easy to eat, high in fat, sugar, and calories, and they stimulate the brain's reward system, making it easy to overeat," she says.
Price and availability also have a major impact on what we buy and eat, she notes.
Structural changes are needed
Aukan finds it troubling that obesity among children, adolescents, and adults in Norway is expected to continue rising – alongside increasing rates of diabetes.
"Physical activity is crucial for health, but if we're going to slow the rise in overweight and obesity, we need structural changes. We have to make it easier for everyone to fill up on healthy, nutritious food – while also reducing exposure to unhealthy, high-calorie options," she argues
Should change public health advice
The study's lead author, Herman Pontzer, was interviewed by the Swedish newspaper Dagens Nyheter.
He said the results of this study should change how public health authorities talk about obesity.
Currently, the World Health Organization (WHO) and many national health agencies say that obesity is a problem related to both food and exercise.
But for most people, diet is much more important than exercise when it comes to losing weight, according to Pontzer.
"Over 90 per cent of the obesity problem is about diet," Pontzer said in the interview.
