When you start an exercise regimen, do you make other lifestyle changes as well? Are you more aware of and intentional about your food choices? Are you more or less physically active throughout the day? Research shows that when people start exercising regularly, they tend to change other behaviors to minimize calories burned outside of their workout times. This phenomenon called "energy compensation" is a collection of behavioral (and biological) adjustments that take place in response to exercise or more aptly, to the threat of weight loss. Some people compensate for the calories burned during their workouts by eating more while some do so by decreasing their physical activity throughout the day. Exercise increases the drive to eat by increasing appetite stimulating hormones while reducing hormones that make you feel full (satiety hormones).
Energy compensation was likely an advantage in the prehistoric era during which, the ability to store energy (in the form of fat or glycogen) was of necessity in order to survive periods in which food was scarce. Body fat is stored energy and those with more of it, are more suited for survival in periods of food shortage or famine as they have more substrate for their bodies to metabolize to meet the energy demands of basic biological needs. Now, for many, though the threat of food deprivation is obsolete, our bodies have not yet fully adapted to this and are still internally wired to prevent the loss of these energy stores vital for survival.
In general, regular exercise alone (when not combined with diet changes) is not very effective for weight loss though studies do show it does produce slight reductions in body weight. Energy compensation contributes to this as those who eat more and/or move less dampen the negative caloric balance needed for weight loss to occur. Negative caloric balance is when calories used (for resting, activity, and digestion) exceed calories consumed in the diet. Researchers have explored whether exercise training volume or the amount of calories burned during each workout can impact the energy compensation response. In one study, weight loss, food intake, and other variables were compared in participants who burned either 300 or 600 calories per day 5 days per week for 12 weeks. They found that energy compensation occurred in both groups (300 and 600 calories per day), but only individuals burning 600 calories per workout lost weight.
Based on these findings, there appears to be a threshold energy expenditure (caloric burn) somewhere around 3,000 calories per week beyond which energy compensation is less effective at preventing weight loss. Participants in this study were young, healthy adults and the 600 calorie-per-day exercise goal was feasible for them given the high compliance rates. However, in some people with joint or muscle pain or in older adults or other populations, burning 600 calories per day might be possible once, but would likely not be feasible to do consistently 5 days per week as this could increase the risk of new or worsening of existing injuries. This could also be difficult for those with low exercise capacity due to low fitness levels. The better approach would be to focus on a combined diet and exercise approach for weight loss goals.
In addition to eating more, energy compensation can be done by reducing movement or physical activity outside of structured exercise. Studies on this component of energy compensation have yielded inconsistent results which could be due to variations in methods and in the age ranges of the study populations. Some studies have shown that people who begin exercise regimens maintain their physical activity outside of their workouts while others have shown that people become less physically active outside of their workout times. The latter has been documented in elderly adults who tend to spend more time sitting on workout days compared to non-workout days. I don't know if this happens when people start practicing yoga, but we're in the process of getting back to a study in our lab in which we're attempting to find out.
Prolonged sitting is to be avoided whether you're exercising regularly or not. Along with increasing the risk of chronic disease, studies show that prolonged sitting outside of exercise diminishes or even cancels out the benefits of exercise. One study found that sitting for 6 hours after a workout resulted in less of a decrease in blood pressure compared with breaking up the sitting with 3-minute bouts of walking. Another study showed that when participants sat most of the day for 4 days before exercise, the exercise session was completely ineffective in inducing the metabolic benefits like lower glucose, triglyceride, and insulin levels after a high fat meal.
Just be aware of your behaviors outside of your exercise time as these can determine how effective your workouts are. Now that the fall semester is off to a good start, I hope to get these out to you more frequently.
Flack KD, Ufholz K, Johnson L, Fitzgerald AS, Roemmich JN. Energy compensation in response to aerobic exercise training in overweight adults. Am J Physiol Regul Integr Comp Physiol. 15(4): R619-R626, 2018.
Kim I, Park S, Chou T, Trombold J, Coyle. Prolonged sitting negatively affects the postprandial plasma triglyceride-lowering effect of acute exercise. Am J Physiol Endocrinol Metab. 311: E891–E898, 2016.
Akins JD, Crawford CK, Burton HM, Wolfe AS, Vardali E, Coyle EF. Inactivity induces resistance to the metabolic benefits following acute exercise. J Appl Physiol. 126(4): 1088-1094, 2019.
Wheeler M, et al. Effect of morning exercise with or without breaks in prolonged sitting on blood pressure in older overweight/obese adults. Hypertension. 73:859-867, 2019.