Increased postprandial energy expenditure in obese women after peroral K- and Mg-phosphate

Energy expenditure (EE) was studied in 15 obese (BMI > 27.5, median 29.2) and 15 lean (BMI < 22.9, median 21.7) healthy, postmenopausal women before and after peroral orange juice with or without K- and Mg-phosphate supplementation. The women, 56-58 years old, were studied in a double-blind, crossover experiment on two separate days. They received 100 ml of orange juice (10 g of carbohydrates) with or without a supplement of K+ (35 mmol), Mg2+ (17 mmol) and HPO4(2-) (39 mmol). Measurements were made before and 30 and 60 min after the stimuli. Intake of juice only had no effect on EE in either the lean or the obese subjects. When the minerals were added, EE (+6.3%; p < 0.001) increased significantly in the obese group with in a maximum 30 min after stimulus, while no such increase was seen in the lean group. The difference between the groups was significant (p < 0.05) and so was the difference in the obese group with or without minerals (p < 0.01). We conclude that an addition of potassium/magnesium-phosphate to glucose increases the postprandial thermogenesis in obese postmenopausal women, but not in lean ones.