The Study
Metabolic flexibility following resistance exercise and a high protein diet in older men: Results from a 12-week randomized controlled trial.
This study is like a fair test where some guys did weight training and others didn’t, and scientists measured how well their bodies switched between burning fat and sugar. Because they randomly picked who did what, we can say weight training probably caused the improvement — but only in these 33 men.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
This study tested if lifting weights and eating more protein help older men’s bodies switch between burning fat and carbs more easily — like a car switching between gas and electric.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 582 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1Yes — better fuel switching means your body handles blood sugar and energy better, which can help prevent type 2 diabetes and fatigue as you age.
- 2Lifting weights twice a week made it easier for men to switch fuels during sleep-wake cycles and after exercise (big improvement).
- 3Eating extra protein helped a little — only during one workout.
- 4The two together didn’t work better than weights alone.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Experimental gerontology
Year
2026
Authors
C. Griffen, D. Renshaw, M. Duncan, A. Dallaway, H S Randeva, M.O. Weickert, John Hattersley
Related Content
Claims (6)
In healthy older men, eating a high-protein meal does not change how the body switches between using carbohydrates and fats for energy in the two hours after eating.
In healthy older men, performing resistance exercise twice a week for twelve weeks increases the body's ability to switch between using different energy sources during changes in metabolic state, such as after fasting or after exercise.
In healthy older men, consuming 1.6 grams of protein per kilogram of body weight per day slightly increases the shift in respiratory quotient during a single submaximal exercise bout, but does not consistently improve other aspects of metabolic flexibility or enhance the effects of resistance exercise.
In healthy older men, combining resistance exercise with a high-protein diet does not produce a greater improvement in metabolic flexibility than resistance exercise alone, based on measurements of npRQ transitions.
In healthy older men, resistance exercise lowers the rate of fuel use during sleep, resulting in increased fat burning during sleep and enhanced metabolic flexibility when switching between rest and activity.
In older adults with muscle loss, consuming protein is linked to reduced ability to switch between fuel sources, changes in how fats are processed, and decreased mitochondrial function.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.