Green tea and protein separately are able to increase diet-induced thermogenesis. Although their effects on long-term weight-maintenance were present separately, they were not additive. Therefore, the effect of milk-protein (MP) in combination with green tea on diet-induced thermogenesis (DIT) was examined in 18 subjects (aged 18–60 years; BMI: 23.0 ± 2.1 kg/m2
). They participated in an experiment with a randomized, 6 arms, crossover design, where energy expenditure and respiratory quotient (RQ) were measured. Green tea (GT) vs.
placebo (PL) capsules were either given in combination with water or with breakfasts containing milk protein in two different dosages: 15 g (15 MP) (energy% P/C/F: 15/47/38; 1.7 MJ/500 mL), and 3.5 g (3.5 MP) (energy% P/C/F: 41/59/0; 146.4 kJ/100 mL). After measuring resting energy expenditure (REE) for 30 min, diet-induced energy expenditure was measured for another 3.5 h after the intervention.
There was an overall significant difference observed between conditions (p
< 0.001). Post-hoc, areas under the curve (AUCs) for diet-induced energy expenditure were significantly different (P
≤ 0.001) for GT + water (41.11 [91.72] kJ·3.5 h) vs.
PL + water (10.86 [28.13] kJ·3.5 h), GT + 3.5 MP (10.14 [54.59] kJ·3.5 h) and PL + 3.5 MP (12.03 [34.09] kJ·3.5 h), but not between GT + 3.5 MP, PL + 3.5 MP and PL + water, indicating that MP inhibited DIT following GT. DIT after GT + 15 MP (167.69 [141.56] kJ·3.5 h) and PL + 15 MP (168.99 [186.56] kJ·3.5 h) was significantly increased vs.
PL + water (P
< 0.001), but these were not different from each other indicating that 15 g MP stimulated DIT, but inhibited the GT effect on DIT. No significant differences in RQ were seen between conditions for baseline and post-treatment. In conclusion, consumption of milk-protein inhibits the effect of green tea on DIT.