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Quantitation of tissue loss during prolonged space flight
The American Journal of Clinical Nutrition
|November 1, 1983
Summary
Astronauts lost significant lean body mass (LBM) and fat during Skylab missions. Over half of the total weight loss was attributed to LBM, with reductions stabilizing after the first month.
Area of Science:
- Space medicine
- Human physiology
Background:
- In-flight body weight loss is a concern for astronauts.
- Understanding body composition changes is crucial for long-duration spaceflight.
Purpose of the Study:
- To analyze lean body mass (LBM) and fat components of inflight body weight loss.
- To evaluate different methods for assessing LBM changes in space.
Main Methods:
- Analysis of data from three Skylab missions involving nine crewmembers.
- Employed six methods to determine LBM based on changes in total body water, potassium, nitrogen balance, and body density.
- Applied corrections to methods relying solely on body potassium and nitrogen balances.
Main Results:
- Mean inflight total body weight loss was 2.7 kg.
- Over half of the weight loss (1.5 kg) was attributed to LBM reduction, including 1.1 kg of body water.
- The remaining 1.2 kg of weight loss was derived from fat stores.
- LBM reduction appeared complete after one month and was independent of mission duration, diet, and exercise.
Conclusions:
- Lean body mass loss is a significant component of astronaut weight loss during spaceflight.
- Standard methods for LBM assessment require correction for accurate in-flight measurements.
- LBM reduction stabilizes early in space missions, suggesting adaptation or a new steady state.