In early October, the latest article by Chaise Murphy, until recently a PhD student in our group, and Prof. Karsten Köhler was published in the Scandinavian Journal of Medicine & Science in Sports. The results of the article titled "Energy deficiency impairs resistance training gains in lean mass but not strength: A meta-analysis and meta-regression" are no longer only found in research circles, also in blogs and Twitter the article was already a topic.
Energy deficits occur when individuals consume too little energy in the form of food (and fluid) relative to their daily energy expenditure. Short-term energy deficits (ED) impair anabolic ("building") hormones as well as muscle protein synthesis, i.e. the building process of muscle mass. However, the extent to which prolonged energy deficits affect resistance training (RT) outcomes remains largely unexplored. Therefore, as part of his current publication, Dr. Murphy investigated whether and to what extent the presence of a food-induced energy deficit, i.e., a deficit achieved by reducing food intake, attenuates training responses induced by resistance training.
Following a systematic literature search through PubMed and SportDiscus for appropriate studies, two analyses were conducted: Using Analysis A, a meta-analysis, changes in lean mass (body lean mass, i.e., body weight minus storage fat) and strength as a result of resistance training with energy deficit (RT+ED) and without energy deficit (RT+CON) were examined. This analysis therefore included only randomized controlled trials, i.e., trials with a control group without energy deficit. Since only a few studies with a control group exist, studies without a control group were also examined in a secondary analysis, Analysis B, and compared with separate RT+CON studies regarding participant and intervention characteristics. Further, gains in LM and strength were qualitatively compared between RT+ED and RT+CON. Subsequently, the two analyses were combined in a meta-regression to examine the relationship between the magnitude of energy deficit and lean mass. The meta-regression showed that an energy deficit of about 500kcal per day prevented the increase in lean mass.
For strength athletes this means that they should avoid a longer energy deficit if they want to build muscle mass. To maintain muscle mass during weight loss, they should take care to avoid energy deficits greater than 500 kcal per day. In addition, the results of both analyses showed that strength training with energy deficit does not affect strength gain.
The question "can I build muscle and lose weight at the same time?" has been asked by strength athletes for a long time, so it is not surprising that Dr. Murphy's findings have generated attention on the Internet and have been picked up by, among others, a very high-traffic sports science and sports nutrition blog, mysportscience.com. In addition, Dr. Murphy has made it into social media and you can also find the article on Twitter or LinkedIn, for example.
For more information, you will find the full-text here.