Effects of one week juice fasting on lipid metabolism: a cohort study in healthy subjects.

OBJECTIVE We investigated the effects of a popular modified juice fasting program on lipid metabolism. VOLUNTEERS AND METHODS 5 healthy, nonobese, male volunteers fasted for 8 days. Daily energy intake was limited to 150-300 kcal/d solely as carbohydrates (vegetable and fruit drinks). Physical activity was maintained as before. At baseline, on days 2, 3, and 8 during fasting, and on days 2 and 8 after fasting, serum lipids, lipoproteins, and insulin were investigated. RESULTS Juice fasting resulted in bi-phasic changes: Until day 2 and 3 triacylglycerols (TG), very low-density lipoprotein apolipoprotein B (VLDL apo B), and insulin decreased by 52, 51, and 65% respectively, while nonesterified fatty acids (NEFA), low-density lipoprotein (LDL) apo B, and LDL cholesterol increased by 363, 38, and 35%. Between day 3 and 8 NEFA increased; TG and insulin increased as well, but remained below baseline values, and LDL cholesterol normalized. After 8 days juice fasting significant changes (p < 0.05) compared to the baseline were found only for free cholesterol (-10%), phospholipids (-14%), apo AI (-9%), apo AII (-11%), insulin (-42%), C-peptide (-57%), and NEFA (+535%, p = 0.0001). Total cholesterol decreased by 9% (n.s.) after 8 days. One week after the ending of fasting all parameters returned to normal. CONCLUSION Contrary to total fasting and fasting with limited physical activity, 8 days juice fasting without limitation of physical activity results in a decrease of free cholesterol and an only initial increase of LDL cholesterol. After 8 days insulin, TG, and VLDL are still lower than at baseline, however, they have increased compared to the initial phase, probably counterregulatory to a further increase of NEFA.