Secrets of the Three Groups Who Never Became Obese
Their stories suggest we were looking in the wrong places for answers.
Posted August 1, 2025 | Reviewed by Davia Sills
As more people become overweight, their health may be seriously compromised. Current attempts to counter weight gain focus primarily on energy input, whether by going on diets or taking drugs to reduce appetite .
Three Groups Resist Overweight
The three groups that never become obese are hunter-gatherers, subsistence farmers, and children of earlier generations. This phenomenon had surprisingly little to do with diet . None of these groups went on a diet. None of them took Wegovy or Ozempic, either. Instead, they practiced a lifestyle that increased energy output rather than limiting energy intake.
Children Who Play Outdoors
Childhood overweight is a modern problem. In earlier generations, overweight children were few and far between. In the past, children were very physically active. Most played outdoors. Modern children spend a lot of time on screens, which limits their mobility, setting them up for weight problems.
Playing outdoors uses energy for several distinct reasons. First, it is a physical activity that requires energy expenditure to power muscles. Second, it is exciting and therefore stimulates the fight-or-flight response of the Sympathetic Nervous System (SNS). The SNS speeds up metabolism in preparation for activity. Third, the SNS stimulates the release of glucagon, which is an energy-consuming hormone . (Glucagon also reduces appetite, which is why it is the target of weight-loss drugs). Fourth, the SNS stimulates brown fat—a tissue specialized for heat generation that protects young mammals from cold exposure. Fifth, being outside exposes children to colder conditions, which activates brown fat.
Parents are often surprised that small children may play for hours in the snow without getting chilled. This may be because their brown fat is more active than it is for adults. Some of these phenomena were also relevant to our remote hunter-gatherer ancestors.
Indigenous peoples studied by anthropologists were universally slender. This was not because they were food-deprived. When their food intake was controlled for body weight, they ate far more than urban people do (1).
Their high food intake was countered by a high level of physical activity that burned off a lot of energy. Although there is wide variation in physical activity levels for different people, most did approximately five to ten times the minimum activity level recommended by the American Medical Association and other authoritative organizations (two and a half hours of vigorous activity per week with three bouts of resistance exercises, such as sit-ups or push-ups).
Hunter-gatherers were exposed to wind, rain, and the cold of nights. Such thermal challenges meant that they would have more active brown fat than most urban dwellers.
Hunter-gatherers typically ate widely spaced meals. Much of their food required preparation, such as breaking nuts, peeling fruit, or cooking meat. So, they would go out in search of food, bring it back to camp, and prepare it before eating. These conditions favored the burning of fat as an energy source.
However much they ate, their lifestyle allowed them to burn off the energy they took in, remaining slender.
Photographic depictions of people in agricultural societies indicate widespread slenderness. Before the transition of most people to urban life, obesity rates were extremely low.
This phenomenon is partly attributable to the level of physical work required on farms. Of course, before about 1950, most workers were physically active. After this time, most jobs, including agricultural ones, became highly mechanized.
Like hunter-gatherers, subsistence farmers spent a lot of time in the open air, stimulating their SNS and generating heat production in brown fat.
Farmers stored more body fat than hunter-gatherers, however, possibly reflecting access to more food, particularly high-calorie foods such as rice and potatoes. One consequence was that women in farming communities accumulated sufficient fat to become pregnant at an earlier age than hunter-gatherers.
Subsistence farmers consumed more food than contemporary urban residents—judging from historical government food production numbers—but had minimal levels of overweight.
Environmental Drivers of Overweight
Modern populations fall far short of medical exercise guidelines that are themselves far less than what subsistence people performed.
Modern diets are also problematic in two key respects that did not apply to pre-1950s diets. One is that large amounts of sugar are added to most of our foods, so that sugar consumption is substantially greater than it was in the past (1). Animal experiments found that putting sugar in the drinking water of rodents makes them obese in a matter of weeks.
Highly processed snack foods are low in fiber, so they pass quickly through the digestive system, allowing snackers to continue eating and take in too much energy. Such “highly-processed” foods increase weight in experiments with human subjects, whereas high-fiber whole foods reduce body weight.
Sugar and junk food are recent challenges and are better avoided. Otherwise, the three groups resisting overweight benefited from increased energy output, whether by physical activity, through stimulating heat production in brown fat, or through widely spaced meals comprised of whole foods.
Barber, N. (2025). Weight loss without diets or drugs. Boyle, Ireland: Trudy Callaghan.
Weight Loss Without Diets or Drugs: Barber, Nigel: 9798281153485: Amazon.com: Books
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Nigel Barber, Ph.D., is an evolutionary psychologist as well as the author of Why Parents Matter and The Science of Romance , among other books.
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This article is part of the Bringwise Psychology Journal — daily insights on human behavior, mental health, and personal growth.