(P24-006-25) Gender-Specific Variations in Fat-Free Mass Preservation and Resting Metabolic Rate Adaptations After Weight Loss

Objectives: There are gender differences in composition of weight loss, and rates of weight loss and regain. In general, weight loss is considered slower and weight regain easier for women compared to men and the difference is attributed mainly to the difference in lean body mass between gender. Nonetheless, there can be inter-individual differences within genders. This hypothesis generating case report compared body composition changes, and resting metabolic rate (RMR) adaptations in a female and a male of similar age, weight loss amount and treatment duration.

Methods: A 40-year-old female and a 41-year-old male were treated for weight loss, using the “Compatibility based, Allocation Focused Progress Monitoring Lifestyle Modification Treatment” (CAP-LMT). After a detailed interview, their personalized diet was planned based on CAP-LMT guidelines. (DOI:10.3109/09637489309017425.) The female participated in the treatment for 28 wk and the male for 23 wk. Body composition and RMR were assessed at baseline and at the end of the intervention by using BOD POD and metabolic cart, respectively.

Results: Female lost 15.2% body weight from a baseline of 90 kg. Fat loss was 41% of the weight lost. RMR dropped from 1953 to 1577 kcal/d. RMR per unit of fat-free mass (FFM) declined from 16.22 to 15.37 kcal/d. Male lost 16.2% body weight from a baseline of 96.8 kg. Fat loss was 94% of the weight lost. RMR dropped from 2489 to 2024 kcal/d. RMR per unit of FFM declined from 20.16 to 16.64 kcal/d.

Conclusions: Both subjects had similar % of total weight loss and about 20% reduction in RMR after weight loss. FFM loss was 5.5 kg for the female and 0.8 kg for the male. However, the male experienced a more pronounced reduction in RMR per unit of FFM. While we acknowledge the anecdotal nature of this case report, we hypothesize that preserving FFM during weight loss may not be adequate in protecting against weight regain. Reduction in RMR per unit FFM may be important to consider in identifying the risk factors for weight regain.

Funding Sources: N/A