Changes in skeletal muscle and organ size after weight loss

The Study

Most people who lose weight have a really hard time keeping it off. This is largely due to a drop in resting energy expenditure after weight loss. The goal of this study was to learn more about the root cause of the metabolic decrease that accompanies weight loss. For this investigation, 53 men and 39 women with type 2 diabetes were randomly assigned to one of two groups. The first group had an intensive diet and exercise intervention to help them lose weight. The second group had diabetes support and education, but did not lose weight. MRI scans were performed on all subjects at the end of one year and then again at the end of the second year.

The results were very interesting. By the end of 1 year, only the diet and exercise group lost weight (14.5 pounds on average). The diet and exercise group lost a bit more muscle during the first year (about ½ a pound), but also had significant reductions in the size of their spleen and liver when compared to the control group. American Journal of Clinical Nutrition 2017; 105:78-84.

Take Home Message

This is a pretty cool study. The intervention that helped these subjects lose weight was really heavy on exercise, which is why they maintained a lot of their muscle. The fact that their organs decreased in size is fascinating. Organs like the liver, spleen, heart, and kidneys burn a lot of calories. The fact that they may get smaller after weight loss may explain a lot of the decrease in metabolic rate seen after weight loss. 

The take home message is the following: lift weights at least twice per week when trying to lose weight. This will minimize the loss of lean muscle tissue and make it much easier to keep the weight you lose off permanently. We need to learn more about the decrease in organ size and how this may impact our ability to keep weight off. Stay tuned.