L-tryptophan does not increase weight loss in carbohydrate-craving obese subjects

Eight subjects, aged 26 to 50 years, who had long histories of carbohydrate (CHO) craving and were more than 45 kg above desirable body weight participated in a randomized, double-blind, cross-over pilot study on the effects of L-tryptophan on weight loss and mood state. One g of tryptophan with 10 g of CHO was administered three times a day, 30 min before meals, as an adjunct to a weight-loss protocol that included nutritional consultation teaching low fat, high fiber diets ranging from 1200-1600 kcals/day, behavior modification, and supportive therapy. During the pretreatment period, body weight and plasma tryptophan levels were measured and the Beck Depression Inventory, SCL 90 rating, and Profile-of-Mood State (POMS) were used to assess mood. During the treatment periods, subjects kept daily records of food intake and the timing of medication. All patients were seen at least bi-weekly. After six weeks on medication, baseline measurements were repeated and the crossover between tryptophan and placebo was implemented. After an additional six weeks on placebo or tryptophan, the same measurements were repeated. For the eight patients who completed the three-month protocol, the mean weight loss for six weeks on placebo was 1.14 kg and for six weeks on tryptophan was 2.3 kg. Mean Beck scores were 8.8 during the control period, 8.3 on placebo, and 10.9 on tryptophan. Mean SCL 90 ratings were 69.2 during the control, 54.6 on placebo, and 64.2 on tryptophan. Mean scores for total mood disturbance on the POMS were 48 during the control period, 43 on placebo, and 52 on tryptophan. None of the differences in the psychometric tests was significant. Plasma L-tryptophan levels were significantly higher during the administration of medication (1.74 mg/dl)than during the placebo period (1.25 mg/dl) (P<0.05), confirming compliance in taking the medication. The administration of three g of L-tryptophan daily to this group of refractory obese subjects resulted in no significant differences in weight loss or alterations in mood state during the period of observation.