The reason exercise alone is so hard to create a caloric deficit is because above moderate exercise activity levels, total energy expenditure plateaus. For example, in a large study of physical activity and 24 energy expenditure, those who had the highest physical activity compensated by reducing their activity in other components (i.e., NEAT)
CARDIO FOR FAT LOSS SUMMARY
- Using cardio for fat loss is one of many way to increase calories burned. Cardio is conjunction with resistance exercise is much more effective for fat loss.
- More exercise can result in a compensation response, although a moderate dose of exercise does not seem to have this effect.
- Some people completely compensate for calories after exercise and lose little weight, and some even gain weight.
When people need to lose weight, they think doing more exercise is best for weight loss goals. If your goal is to lose fat, healthier eating, burning more calories, and strength training can contribute to long-term weight loss. The role of exercise is generally considered secondary to caloric restriction for treating obesity.(1) Aerobic exercise has often been the preferred choice of exercise for healthy weight loss, but without diet, the results in body fat are often small, and some studies have found no changes in body weight.(2-4)
To achieve the long-term goal of clinical weight loss (>5% body weight), one would need to perform 225 to 420 minutes of aerobic exercise per week.(5) Exercise alone is so hard to create a caloric deficit because above moderate exercise activity levels, total energy expenditure plateaus.
For example, in a large study of physical activity and 24 energy expenditure, those with the highest physical activity compensated by reducing their activity in other components (i.e., non-exercise adaptive thermogenesis or NEAT).(6) Activity thermogenesis or NEAT refers to the number of calories you burn outside the gym. For example, walking, house chores, etc.
Adaptive thermogenesis refers to the decrease in metabolic rate with weight loss beyond what can be predicted from the loss of body weight and the corresponding changes in fat and lean tissues. The concept of adaptive thermogenesis attempts to explain why weight loss eventually plateaus while dieting.
Adaptive Thermogenesis Principles
Compensation responses to exercise can be divided into two categories:
1.) Automatic compensatory responses are responses that we have no control over, such as reduced metabolic rate or REE, when faced with an energy deficit.
2.) On the other hand, behavioral compensatory responses are those over which individuals have control, such as eating more food (i.e., increased calories), which is believed to be the primary compensatory response when the body is faced with an energy deficit induced by exercise.
CAN I EAT WHATEVER I WANT AND STILL LOSE WEIGHT?
Appetite is highly variable; some people eat more after exercise, and others don’t.(7) Some people are classified as compensators, whereas others are classified as non-compensators. Compensators are motivated to exercise so they can eat after exercise, prefer high-fat, sugary foods, and derive pleasure from food after exercise.(8)
To demonstrate the large variability in compensation response to exercise, 530 women were randomized to either 150, 225 or 300 minutes a week of aerobic exercise for 12 months with no diet; they were allowed to eat their normal diet.
Approximately 9% of the women lost more weight than expected, 20% compensated by 0–50% (i.e., lost slightly less weight than predicted), and ~44% compensated by 50 to 100% (i.e., experienced minimal weight loss compared to what was predicted). Shockingly, close to 27% of the women had >100% compensation and gained weight!(9)
A literature review found that actual weight loss is roughly 30% of the calculated estimated weight loss.(10) What factors make people compensate for consuming more calories after exercise? The greatest predictors of increased compensation are the starting body fat(e.g., those with lower bodyfat compensate more than those with higher body fat), age, and duration of the diet (i.e., short-term duration (<25 weeks usually leads to a negative compensation, but as the diet persists >25 weeks, greater compensation occurs).(11)
CARDIO FOR FAT LOSS. IS IT EFFECTIVE?
Physical activity decreases with increasing age; on average, physical activity decreases after 50 years of age.(12) Two studies have found that exercise resulted in a 50% compensation response or roughly 1,000 kcals per week in response to exercise regardless of the duration or frequency.(13) In general, most studies show that exercise increases some form of food compensation, but the good news is that it’s still creating a caloric deficit for weight loss.
Thus, increasing exercise leads to a constrained total energy expenditure. They would sit instead of standing, fidget less, etc. Researchers assigned 171 subjects to a moderate exercise (burn ~700 kcals per week) or a high exercise (burn ~1760 kcal per week) group. At the end of the study, both exercise groups increased compensation-related energy intake by eating more.
The more shocking findings were that almost half (42.4%) of the subjects in the 700 kcal exercise groups and 23.5% of participants in the 1760 kcal exercise groups did not lose any weight or gained weight.(14) This suggests that exercise alone results in compensation activities such as eating more or reducing NEAT. If weight loss is your goal, track your progress by recording the calories burned in the gym, but keep track of your calories outside the gym with a step counter.
In a study of various athletes over the course of a competitive season (i.e., basketball players, swimmers, volleyball, triathlons), despite the athletes increasing physical activity thru their respective sports, their weight remained relatively stable over the course of the season, suggesting a large increase in food compensation. The average calorie intake over the season was 4,228 calories.
Despite the increases in physical activity, there was no reduction in metabolic adaptations, suggesting the athletes were in a neutral energy balance. A different story occurred when the researchers looked at the athletes by individual sports. Basketball players had an increase in resting energy expenditure of 10%, but they ate far more calories than the other athletes, suggesting a caloric surplus.
Contrary, the triathletes had a decrease in resting energy expenditure, and there was a negative trend in calorie consumption. The triathletes had the greatest increase in physical activity compared to the other sports (54% increase) and the lowest energy intake (-38.5%) compared to the other sports. Thus, those athletes that were in a caloric surplus were able to have positive metabolic adaptations over the course of the season. In contrast, others who were in a negative caloric balance had a negative metabolic adaptation.(15)
Cardio for Fat Loss-Are There Other Alternatives?
Cardio for fat loss is just a tool for increasing energy expenditure, but the combination of cardio and diet restriction provides comparable weight loss if they provide similar levels of negative energy balance. For example, 35 healthy overweight men and women were placed into two weight-loss groups: weight loss thru diet alone (i.e., 25% reduction in energy intake) and exercise and caloric restriction (i.e., a 12.5% reduction in energy intake plus a 12.5% increase in exercise energy expenditure).
After 24 weeks, the two groups had similar weight loss (by about 10%) and similar visceral fat loss (by about 25%). However, the exercise and diet group had superior increases in health parameters such as improved cardiovascular fitness, total serum cholesterol(decrease by 9%), LDL cholesterol (decrease by 13%), insulin sensitivity (increase by 66%), and diastolic blood pressure (decrease by 5%).(16)
Exercise alone is universally seen as a weight maintenance strategy rather than a weight loss strategy. People who successfully maintained weight loss reported spending an average of >60 minutes of moderate-intensity exercise or >35 minutes of high-intensity exercise daily.(17)
Exercise contributes to a healthier lifestyle in conjunction with a healthy eating plan. However, exercise alone is not going to contribute to meaningful weight loss. Most people reduce their other activity levels when exercise increases.
Non-exercise activity thermogenesis (NEAT) is the major contributor to calories burned over the day. NEAT is the calories burned walking to work, typing, performing yard work, undertaking agricultural tasks, and fidgeting.
CARDIO FOR FAT LOSS KEY POINTS
· More exercise can result in a compensation response, although a moderate dose of exercise does not seem to have this effect.
· Some people completely compensate for calories after exercise and lose little weight, and some even gain weight.
3. Church TS, Martin CK, Thompson AM, Earnest CP, Mikus CR, Blair SN. Changes in weight, waist circumference and compensatory responses with different doses of exercise among sedentary, overweight postmenopausal women. PLoS One. 2009;4(2):e4515.
4. Franz MJ, VanWormer JJ, Crain AL, Boucher JL, Histon T, Caplan W, et al. Weight-loss outcomes: a systematic review and meta-analysis of weight-loss clinical trials with a minimum 1-year follow-up. J Am Diet Assoc. 2007;107(10):1755-67.
5. DONNELLY JE, BLAIR SN, JAKICIC JM, MANORE MM, RANKIN JW, SMITH BK. Appropriate Physical Activity Intervention Strategies for Weight Loss and Prevention of Weight Regain for Adults. Medicine & Science in Sports & Exercise. 2009;41(2):459-71.
6. Pontzer H, Durazo-Arvizu R, Dugas LR, Plange-Rhule J, Bovet P, Forrester TE, et al. Constrained Total Energy Expenditure and Metabolic Adaptation to Physical Activity in Adult Humans. Curr Biol. 2016;26(3):410-7.
9. McNeil J, Brenner DR, Courneya KS, Friedenreich CM. Dose–response effects of aerobic exercise on energy compensation in postmenopausal women: combined results from two randomized controlled trials. International Journal of Obesity. 2017;41(8):1196-202.
14. Martin CK, Johnson WD, Myers CA, Apolzan JW, Earnest CP, Thomas DM, et al. Effect of different doses of supervised exercise on food intake, metabolism, and non-exercise physical activity: The E-MECHANIC randomized controlled trial. The American Journal of Clinical Nutrition. 2019;110(3):583-92.
16. Larson-Meyer DE, Redman L, Heilbronn LK, Martin CK, Ravussin E. Caloric Restriction with or without Exercise: The Fitness versus Fatness Debate. Medicine & Science in Sports & Exercise. 2010;42(1).