Key Points
- Diet is most effective for weight/fat loss when compared to exercise.
- Exercise improves results for fat loss and maintenance of a healthy weight.
- Resistance training is more effective than aerobic exercise for fat-loss and body-composition improvements.
Exercise is considered ineffective for weight management and fat-loss by many, and diet is often considered THE only effective method for losing fat. However, the bidirectional relationships between every health facet, from sleep to stress, diet, exercise, and our psychosocial state, suggest that this idea is incomplete at best.
While it’s true that in shorter-term studies (<6 months) there is little difference in effects between diet or exercise + diet interventions for weight and fat loss and superior results for diet-only compared to exercise-only regimens.1 In studies of longer durations (up to 52 weeks), diet and exercise were significantly more effective for weight loss than diet alone,1, 2 while weight regain (around 50% of that lost) after 1 year was not significantly different between interventions.2 This demonstrates that exercise when added to diet has significant and lasting benefits to body composition, likely to be even greater when these can be maintained.
Exercise when added to diet has significant and lasting benefits to body composition
It has also been suggested that the focus for exercise should be on increasing overall metabolic stress from higher intensity forms of exercise (e.g. >70% maximum heart rate) and that resistance training, should be the focus for fat loss.3 Moderate-intensity aerobic exercise effectively reduces body weight (by around 2 kg over 6-12 months) and reduces waist circumference.4 However, compared with aerobic exercise alone, resistance + aerobic exercise results in greater reductions in fat mass, LDL cholesterol, and greater increases in lean mass.5
The focus for exercise should be on increasing overall metabolic stress
In a 2015 meta-analysis by James Clark in the Journal of Diabetes and Metabolic Disorders, diet plus exercise had the greatest effect on fat-loss but diet plus resistance training had a greater effect than diet plus aerobic exercise OR diet plus combined aerobic plus resistance. Resistance training also had a greater independent effect than aerobic or aerobic + resistance.3 These results combined suggest that a healthy diet is essential for healthy weight maintenance and body composition but that exercise improves results, with the greatest effect seen from resistance (weight) training.
Interestingly, despite subjective reports of substantial inter-individual differences in weight change resulting from exercise interventions, the evidence is limited for clinically meaningful individual differences in weight change from exercise.6
Exercise improves results, with the greatest effect seen from resistance (weight) training
Weight-loss maintenance.
After completion of low- or very-low-calorie diets, anti-obesity drugs, meal replacements, and high-protein diets improved weight-loss maintenance, whereas exercise did not.7 This should be interpreted with some caution as the studies reviewed showed improved maintenance of weight loss except in a study which included only knee-joint exercises for arthritis,8 which would be unlikely to provide a high metabolic imperative for improved weight maintenance, and in a study utilising resistance exercise likely to increase lean body mass (and thus mitigate weight-loss effects).9
References
1. Johns DJ, Hartmann-Boyce J, Jebb SA, Aveyard P. Diet or Exercise Interventions vs Combined Behavioral Weight Management Programs: A Systematic Review and Meta-Analysis of Direct Comparisons. Journal of the Academy of Nutrition and Dietetics. 2014;114(10):1557-68.
2. Curioni CC, Lourenço PM. Long-term weight loss after diet and exercise: a systematic review. International Journal of Obesity. 2005;29(10):1168-74.
3. Clark JE. Diet, exercise or diet with exercise: comparing the effectiveness of treatment options for weight-loss and changes in fitness for adults (18–65 years old) who are overfat, or obese; systematic review and meta-analysis. Journal of Diabetes & Metabolic Disorders. 2015;14(1):31.
4. Thorogood A, Mottillo S, Shimony A, Filion KB, Joseph L, Genest J, et al. Isolated Aerobic Exercise and Weight Loss: A Systematic Review and Meta-Analysis of Randomized Controlled Trials. The American Journal of Medicine. 2011;124(8):747-55.
5. García-Hermoso A, Ramírez-Vélez R, Ramírez-Campillo R, Peterson MD, Martínez-Vizcaíno V. Concurrent aerobic plus resistance exercise versus aerobic exercise alone to improve health outcomes in paediatric obesity: a systematic review and meta-analysis. British Journal of Sports Medicine. 2018;52(3):161.
6. Williamson PJ, Atkinson G, Batterham AM. Inter-individual differences in weight change following exercise interventions: a systematic review and meta-analysis of randomized controlled trials. Obesity Reviews. 2018;19(7):960-75.
7. Johansson K, Neovius M, Hemmingsson E. Effects of anti-obesity drugs, diet, and exercise on weight-loss maintenance after a very-low-calorie diet or low-calorie diet: a systematic review and meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition. 2013;99(1):14-23.
8. Christensen P, Frederiksen R, Bliddal H, Riecke BF, Bartels EM, Henriksen M, et al. Comparison of three weight maintenance programs on cardiovascular risk, bone and vitamins in sedentary older adults. Obesity. 2013;21(10):1982-90.
9. Borg P, Kukkonen-Harjula K, Fogelholm M, Pasanen M. Effects of walking or resistance training on weight loss maintenance in obese, middle-aged men: a randomized trial. Int J Obes Relat Metab Disord. 2002;26(5):676-83.
