Why the Same Workout Works Differently for Different Bodies Why do some people burn more energy doing the same activity, while others seem to conserve it? In this episode of AUB at Work, sports nutrition researcher Elie-Jacques Fares explains why the same workout, diet, or supplement plan can produce very different results from one person to another. Fares, assistant professor of clinical and sports nutrition in the Department of Nutrition and Food Sciences at the American University of Beirut, studies how bodies burn and conserve energy. His research looks at exercise efficiency, body composition, and the tools scientists use to better understand how each person’s body responds to movement, training, nutrition, and supplementation. The conversation begins with a surprising finding from one of Fares’s studies: when participants were compared while sitting and standing, only about 20 percent burned more energy while standing. The rest were “energy savers,” whose bodies performed the same task without spending more calories. That finding opens up a broader discussion about why energy expenditure is more complex than we often assume. Two people can appear to be doing the same exercise or movement, but internally, their bodies may be doing very different amounts of work. Fares also explains why exercise efficiency is not inherently good or bad. For endurance athletes, becoming more efficient can help conserve energy during long events. But for people trying to lose weight, too much adaptation to the same workout may reduce how much energy the body burns over time. He also discusses why nutrition and exercise plans should be tested individually, why athletes experiment with diet and supplements before major competitions, and why everyday exercisers should change one variable at a time when trying something new. The episode also explores body composition tools, including machines such as InBody, Tanita, and Seca, as well as bioelectrical impedance vector analysis, or BIVA. Fares explains how BIVA looks beyond basic estimates of fat mass and muscle mass to examine raw electrical values that can offer insight into hydration, cellular health, and how the body changes over time. Finally, Fares discusses where his research is headed next, including projects using stable isotopes to measure energy expenditure and body composition with greater precision, and studies examining how metabolism, fat mass, muscle mass, and activity patterns may interact with long-term health risks such as cardiovascular disease. In this episode: Why standing does not necessarily burn more energy than sitting What it means to be an “energy spender” or an “energy saver” Why two people doing the same workout may burn different amounts of energy How exercise efficiency can help endurance athletes but complicate weight-loss efforts Why nutrition and supplement plans should be tested individually How to track whether a new diet, exercise routine, or supplement is working What body composition tools can and cannot tell us How BIVA may offer a more precise picture of hydration, body composition, and cellular health How Fares’s research could lead to more personalized nutrition, exercise, and health recommendations Featured expert: Elie-Jacques Fares Assistant Professor of Clinical and Sports Nutrition Department of Nutrition and Food Sciences American University of Beirut Listen to learn why there may be no such thing as a one-size-fits-all workout—and why understanding how your own body uses energy could shape the future of exercise, nutrition, and health.
