In
depressive disorders an association between basal pre-treatment plasma ratios of
tryptophan (Trp) and
tyrosine (Tyr) to other large
neutral amino acids (LNAA) and the clinical efficacy of serotonergic acting drugs have been established. In order to clarify whether a similar relation exists in
obesity and to elucidate the long-term effect of
dexfenfluramine (dF) on plasma
amino acid profiles and macronutrient selection, we examined 29 obese patients participating in a 12 months double-blind
weight loss trial with either
dexfenfluramine (dF) (30 mg/day) or placebo (PL) in conjunction with 4.2-5.0 MJ/d diet. Maximum
weight loss was obtained after 6 months (dF 12.8 +/- 5.4 kg; PL 13.8 +/- 9.2 kg, x +/- s.d., ns). Plasma Trp/LNAA and Tyr/LNAA were found to be lower than in normal weight controls and were further reduced during treatment (p < 0.05), but without differences between dF and PL groups. Macronutrient selection was not affected by the dF treatment. In the placebo group
weight loss was associated with a high pre-treatment energy intake and a high
carbohydrate-
protein ratio (p < 0.05). A decrease in
dietary fat and increase in
protein intake (%) and age was found to explain 82% of the variation in
weight loss (p < 0.0005), whereas no correlation could be shown in the dF group. Pre-treatment plasma Trp/LNAA or Tyr/LNAA and
weight loss were not correlated. In conclusion, neither food selection nor basal plasma
amino acid profiles were predictors of
weight loss during long-term treatment with dF as an adjuvant to energy restriction, and they were not affected by the
drug treatment.