People can be in an energy deficit, which means they are eating fewer calories than they need to keep their weight and keep their bodies running at their best, for a number of reasons. Most of the time, people who want to lose weight limit their caloric intake on purpose. Athletes, on the other hand, may be in an energy deficit because of disordered eating, increased training, or unintentional undereating.

Can lifting weights help you lose weight?

‍In recent years, a lot of research has shown that resistance training is good for people who are trying to lose weight. If calorie restriction is combined with resistance training, lean mass and bone are preserved during weight loss and weight gain is slowed. But the other side of this question hasn't been thought about much. That is, what happens when we do resistance training when we don't have enough energy vs. when we do it when we have enough energy, or even when we have too much energy, as is often recommended?

Can a lack of energy make resistance training less effective?

‍We published a study last year that showed a hormone response was lessened when heavy resistance exercise was done after only two days of not getting enough food. But it is not known what the long-term effects of training in an energy deficit are. So, we built on this finding in a recent meta-analysis that looked at changes in lean mass and strength after resistance training with and without a prescribed energy deficit. But there aren't many studies that include both groups who did resistance training when their energy was low and groups who did it when their energy was normal. So, to increase the size of the sample, we matched groups of participants from different studies based on their gender, age, and training parameters (such as the number of sets and repetitions) so that we could compare their effects in a second analysis.

In both of our studies, our results showed that resistance training in a low-energy state makes it harder to gain lean mass as a result of resistance training. When energy was balanced, strength training always led to gains in lean mass. However, when energy was low, strength training always led to a loss in lean mass. We plotted the change in lean mass against the energy deficit to find a threshold. On average, an energy deficit of 500 kcal per day did not cause a loss or gain in lean mass.

No matter how much their average lean mass changed, whether they were in an energy deficit or not, the people in the study got stronger. Several studies showed that people lost a lot of lean mass (1-2 kg), but they still gained a lot of strength (25-50% of their one-repetition maximum), just like people in groups that didn't have an energy deficit. When trying to figure out what these results mean, it's important to remember that almost all of the studies were done on sedentary people who gain a lot of strength quickly at the start of a resistance training program. There is a chance that experienced lifters don't see the same strength gains, but the current analysis didn't have enough data on trained people to answer this question.

Conclusion

‍So, what can we learn from these findings? If you do resistance training to build lean muscle, a lack of energy will slow your progress. If you have to be low on energy, don't go below 500 kcal per day. If you want to get stronger, an energy deficit probably won't hurt your progress, at least when you first start resistance training. For experienced lifters, it's still too early to tell.

Prevess is providing an app, that automates the decision for you and your athletes of the team, so that you always make the right decision.

References

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2. 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.
3. 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.
4. 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.

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