Hormonal and metabolic adaptation to protein-supplemented fasting in obese subjects

Thirty hospitalized, severely obese patients (40 +/- 2 yr, 82 +/- 4 percent weight excess) were submitted to a 13-d protein-supplemented fast (PSF) with 70 g milk proteins/d (1.26 MJ or 300 kcal). The mean weight loss during PSF was 5.4 +/- 0.3 kg corresponding to 422 +/- 39 g/d. Comparison of the urinary nitrogen excretion with daily protein intake revealed that the nitrogen balance was equilibrated during PSF. Blood glucose decreased moderately but significantly during the whole PSF period whereas plasma insulin was only reduced during the first 9 d and tended to rise thereafter. Plasma FFA increased rapidly and remained elevated until the end of the study (+ 60 per cent); serum total cholesterol and plasma triglycerides showed a 26 and a 35 per cent decrease respectively. Basal plasma glucagon was slightly increased. Due to the low sodium intake (42 mmol/d) urinary sodium excretion dropped rapidly. Simultaneously both systolic (-13 mmHg) and diastolic (-7 mmHg) arterial blood pressure decreased significantly. The biological tolerance was good: metabolic acidosis was prevented with sodium bicarbonate, excessive rise in serum uric acid was corrected with allopurinol and a marked decrease in serum potassium was avoided with an appropriate dose of spironolactone. Twenty-six patients could be weighed 6 to 15 months after PSF: 12 showed a further weight reduction (6.6 +/- 1.6 kg) and seven a discrete weight gain (1.0 +/- 0.4 kg). Thus, PSF was well accepted and was profitable in 19 out of our 30 patients. It should be restricted to cases of severe and refractory obesity and performed under careful medical supervision.