Indoxyl sulfate as a biomarker of prebiotic efficacy for weight gain prevention

A method for predicting and/or quantifying the response of a subject to prebiotics in the prevention of diet induced weight gain, comprising:

• a) determining a level of indoxyl sulfate in a urine sample obtained from a subject that has consumed prebiotics using 1H-NMR spectroscopy or mass spectroscopy, and
• b) comparing the subject's indoxyl sulfate level to a predetermined reference value by mapping or graphing the urinary excretion of indoxyl sulfate,
• wherein a decreased indoxyl sulfate level, or an absence of change in the indoxyl sulfate level, in the urine sample compared to the predetermined reference value indicates that the administration of prebiotics is effective in the prevention of diet induced weight gain in the subject,
• and wherein the predetermined reference value is based on an average indoxyl sulfate level in a control population of subjects consuming a high fat diet and the change of indoxyl sulfate level is determined relative to a cut-off value.