Background/Objectives: EFFORT: Asthma study is a randomized controlled trial designed to assess the effects of diet and exercise in non-obese, untrained patients with asthma. We here present results from a subgroup of participants in the diet and control group to assess the feasibility of a high protein and low glycemic index (GI) diet and the effects on body composition.

Subjects/Methods: Of the 149 subjects who were included in the study, 76 subjects (30 males) were randomized into either a diet group (n = 38) or a control group (n = 38) and included in the present analysis. The 8 week intervention consisted of a high protein and low GI diet whilst the control group continued habitual diet.

Results: Thirty-three patients in the diet and 34 in the control group completed the study. The diet group reduced their energy intake by ~20% and had high dietary compliance. Intake of fatty fish doubled and GI was reduced by 8.4 units. The diet group reduced their weight by 2.3 ± 2.2 kg vs. 0.5 ± 1.8 (p < 0.001), fat mass by 2.2 ± 2.0 kg vs. 0.3 ± 1.6 kg (p < 0.001) and preserved lean body mass (-0.02 ± 1.1 kg). The control group had no changes in body composition.

Conclusions: The ad libitum high protein-low GI diet resulted in a greater loss of fat mass among non-obese patients with asthma. The subjects were satisfactory and highly compliant with the dietary regimen.