One may find themselves in an energy deficit, that is, eating fewer calories than is required to maintain weight and optimal physiological function, for a number of reasons. Most commonly, people intentionally restrict caloric intake to lose weight, but athletes may also find themselves in an energy deficit as a result of disordered eating behaviors, their increased training expenditure or unintentional undereating.
Can resistance training aid weight loss?
In recent history, a substantial body of evidence has highlighted the benefits of performing resistance training during weight loss. Compared to caloric restriction alone, adding resistance training to caloric restriction preserves lean mass and bone during weight loss (1) and attenuates weight regain (2). However, the flipside of this question has not been considered often. That is to say, what happens when we resistance train in an energy deficient state compared to resistance training in energy balance, or even surplus, as is often recommended?
Can an energy deficit attenuate adaptations to resistance training?
Last year, we published a study showing that performing a bout of heavy resistance exercise after as little as two days of energy deficiency produced a blunted hormone response (3). However, the long-term effects of training in an energy deficit are unknown. Thus, we built on this finding in a recent meta-analysis (4) evaluating changes in lean mass and strength as a result of resistance training with and without a prescribed energy deficit. However, few studies have both groups who resistance trained in an energy deficit and groups who resistance trained at energy balance. Thus, to expand the sample size, we matched such groups between studies based on participant sex, age and training parameters (e.g., frequency, sets, repetitions) to compare their effects in a secondary analysis.
In both analyses, our results showed that resistance training in an energy deficit impairs the ability to accrue lean mass in response to resistance training. While resistance training at energy balance always led to gains in lean mass, resistance training in an energy deficit, on average, resulted in a loss of lean mass. Because the included energy deficits were of differing strengths, we plotted the change in lean mass against the energy deficit to determine a threshold, and we observed that, on average, an energy deficit of 500 kcal per day resulted in neither a loss nor a gain in lean mass.
... resistance training in an energy deficit impairs the ability to accrue lean mass in response to resistance training.
Regardless of the participants’ average changes in lean mass, they gained strength whether they were in an energy deficit or not. Several studies reported substantial losses of lean mass (~1-2 kg) but still showed participants gaining large amounts of strength (~25-50% of one-repetition maximum) similar to those in the groups without an energy deficit. When interpreting these findings, it is important to consider that almost all studies were conducted in sedentary individuals who rapidly gain large amounts of strength at the onset of a resistance training program. Experienced lifters may not experience the same increases in strength, but the present analysis lacked sufficient data on trained individuals to answer this question.
Conclusion
So, what can we take away from these results? If you conduct resistance training to gain lean mass, an energy deficit will impair your gains. If you must be in an energy deficit, keep it moderate (<500 kcal per day). If you are interested in gaining strength, an energy deficit will most likely not impair your gains, at least when you are new to resistance training. For veteran lifters, the jury is still out.
If you conduct resistance training to gain lean mass, an energy deficit will impair your gains.
References
Villareal DT, Chode S, Parimi N, Sinacore DR, Hilton T, Armamento-Villareal R, Napoli N, Qualls C, Shah K. Weight loss, exercise, or both and physical function in obese older adults. N Engl J Med. 2011 Mar 31;364(13):1218-29. doi: 10.1056/NEJMoa1008234. PMID: 21449785; PMCID: PMC3114602.
Hunter GR, Brock DW, Byrne NM, Chandler-Laney PC, Del Corral P, Gower BA. Exercise training prevents regain of visceral fat for 1 year following weight loss. Obesity (Silver Spring). 2010 Apr;18(4):690-5. doi: 10.1038/oby.2009.316. Epub 2009 Oct 8. PMID: 19816413; PMCID: PMC2913900.
Murphy C, Koehler K. Caloric restriction induces anabolic resistance to resistance exercise. Eur J Appl Physiol. 2020 May;120(5):1155-1164. doi: 10.1007/s00421-020-04354-0. Epub 2020 Mar 31. Erratum in: Eur J Appl Physiol. 2021 Oct;121(10):2941. PMID: 32236752; PMCID: PMC8233264.
Murphy C, Koehler K. Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression. Scand J Med Sci Sports. 2021 Oct 8. doi: 10.1111/sms.14075. Epub ahead of print. PMID: 34623696.
