OBJECTIVE: The dose-response effects of exercise training on insulin sensitivity, metabolic risk, and quality of life were examined.

METHODS: Sixty-one healthy, sedentary (VO₂max: 35 ± 5 ml/kg/min), moderately overweight (BMI: 27.9 ± 1.8), young (age: 29 ± 6 years) men were randomized to sedentary living (sedentary control group; n = 18), moderate (moderate dose training group [MOD]: 300 kcal/day, n = 21), or high (high dose training group [HIGH]: 600 kcal/day, n = 22) dose physical exercise for 11 weeks.

RESULTS: The return rate for post-intervention testing was 82-94% across groups. Weekly exercise amounted to 2,004 ± 24 and 3,774 ± 68 kcal, respectively, in MOD and HIGH. Cardiorespiratory fitness increased (P < 0.001) 18 ± 3% in MOD and 17 ± 3% in HIGH, and fat percentage decreased (P < 0.001) similarly in both exercise groups (MOD: 32 ± 1 to 29 ± 1%; HIGH: 30 ± 1 to 27 ± 1%). Peripheral insulin sensitivity increased (P < 0.01) (MOD: 28 ± 7%; HIGH: 36 ± 8%) and the homeostasis model assessment of insulin resistance decreased (P < 0.05) (MOD: -17 ± 7%; HIGH: -18 ± 10%). The number of subjects meeting the criteria of the metabolic syndrome decreased by 78% in MOD (P < 0.01) and by 80% in HIGH (P < 0.05). General health assessed by questionnaire increased similarly in MOD (P < 0.05) and HIGH (P < 0.01).

CONCLUSIONS: Only minor additional health benefits were found when exercising ∼3,800 as opposed to ∼2,000 kcal/week in young moderately overweight men. This finding may have important public health implications.