New research finds no link between exercise and weight loss

Going to the gym to lose weight? New research says you might want to rethink that plan. A Duke University study found that people who exercise regularly burn about the same number of daily calories as those who rarely leave their desks. This proves that there’s no link between exercise and weight loss. 

In his research, Herman Pontzer, an evolutionary anthropologist at Duke University, discovered that hunter-gatherers from Tanzania's Hadza tribe, despite their highly active lifestyle, burn roughly the same number of daily calories as sedentary office workers in the United States when accounting for body size.

"That was unexpected," said Pontzer, who authored the 2021 book "Burn" about metabolism science. His research led to the development of the "constrained total energy expenditure model," which suggests the human body adjusts its calorie-burning mechanisms to maintain consistent energy expenditure levels regardless of activity.

The model explains why exercise and weight loss are not interlinked. According to Pontzer's research, people who maintain very active lifestyles ultimately burn similar numbers of calories as those who are largely sedentary, though exercise provides other health benefits.

This finding represents one of several metabolism-related discoveries that contradict long-held assumptions about how the human body processes energy. Pontzer's research also disputes common beliefs about gender differences in metabolism and age-related metabolic changes.

Many people think men naturally have faster metabolisms than women, but that's not true. According to Pontzer, men tend to burn more calories because they’re usually bigger and have less body fat. Men and women with similar size and body composition burn about the same amount of energy each day.

The research also challenges the widely accepted notion that metabolism significantly slows during middle age. Studies of thousands of adults between their 20s and 50s showed no meaningful changes in metabolic rate when controlling for body size. According to the findings, notable decreases in metabolism typically begin after age 60.

"If it's not the energy-burned side of the equation, it must be the energy we're eating," Pontzer said regarding middle-age weight gain. He pointed to factors such as stress and seasonal eating patterns as potential contributors to weight changes over time.

The study reveals that young kids, especially three- and four-year-olds, have the most active metabolisms as their bodies are working with energy as they grow and develop. However, due to their small size, they don't burn as many total calories as older kids or adults.

Metabolism, as defined by Pontzer, encompasses all cellular activity within the body's 37 trillion cells, measured in terms of required energy. This complex system operates differently than previously understood, with implications for weight management strategies and public health recommendations.

The research team's findings stem from extensive studies, including the 2012 investigation of the Hadza tribe and subsequent research involving participants across various activity levels, from ultra-marathon runners to individuals leading predominantly inactive lifestyles.

"We've done studies where we look at people who are really active," Pontzer said. "And people who are really sedentary, and actually they're burning the same number of calories."

The body's ability to adjust its energy expenditure explains why increasing physical activity does not necessarily translate to greater overall calorie burn. When someone adopts a more active lifestyle, their body compensates by reducing energy expenditure in other areas, maintaining a relatively stable total daily calorie burn.

These metabolic adjustments include decreased inflammation and stress reactivity, which may contribute to the health benefits associated with regular exercise, even in the absence of significant weight loss.

The research indicates that various dietary approaches, including high-carbohydrate, low-carbohydrate, low-fat, and high-protein diets, show no measurable effect on daily calorie expenditure. Additionally, mental exertion, despite the brain's high energy consumption of about 300 kilocalories per day, does not increase overall calorie burn.

Weight gain patterns observed in middle-aged adults appear to be more closely linked to eating habits than metabolic changes. The research suggests that seasonal weight fluctuations, particularly during holidays, combined with age-related changes in stress levels and eating behaviors, may contribute more significantly to weight gain than previously recognized metabolic factors.

According to the research, the highest total calorie burn typically occurs during late adolescence. However, when measuring metabolic rate relative to body size, young children demonstrate the most intense metabolic activity, challenging previous assumptions about teenage metabolism.

These findings have important implications for public health messaging and weight management programs. While exercise remains crucial for overall health, including cardiovascular fitness, muscle strength, and mental well-being, its role in weight loss may need to be reconsidered.

The research suggests that weight management strategies focusing solely on increased physical activity may need reconsideration. The findings indicate that dietary choices play a more crucial role in weight control than previously thought, though exercise maintains its importance for overall health and disease prevention.

Pontzer's work continues to reshape the scientific understanding of human metabolism, challenging conventional wisdom about energy expenditure and weight management. The research emphasizes the complexity of human metabolism and highlights the need for a more nuanced approach to weight management strategies.

These findings suggest that while exercise provides numerous health benefits, dietary choices may have a more direct impact on weight control than physical activity alone for the average person seeking to manage their weight.

The research appears to explain why many people struggle to lose weight through exercise despite maintaining consistent workout routines. It offers new insights into the relationship between physical activity and weight management and potentially leads to more effective approaches to weight control and public health recommendations.