Migraine, particularly migraine with aura, and increased body weight are independent risk factors for cardiovascular disease (CVD). The association of weight change and clinical markers of CVD risk was evaluated in subjects participating in a randomized double-blind, parallel-group study of migraine-preventive treatment comparing 100 mg/day of topiramate and amitriptyline. Individuals from both treatment groups were pooled and stratified into three groups. The 'major weight gain' group gained > or = 5% of their baseline body weight at the conclusion of the study; the 'major weight loss' group lost > or = 5% of their baseline body weight. The third group had < 5% of weight change. The influence of weight change in headache outcomes, as well as in markers of CVD (blood pressure, cholesterol, C-reactive protein), was assessed using analysis of covariance. Of 331 subjects, 52 (16%) experienced major weight gain and 56 (17%) experienced major weight loss. Weight change was not associated with differential efficacy for the treatment of headache. However, contrasted with those with major weight loss, those who gained weight experienced elevations in mean diastolic blood pressure (+2.5 vs. -1.2 mmHg), heart rate (+7.6 vs. -1.3 beats per minute), glycosylated haemoglobin (+0.09% vs. -0.04%), total cholesterol (+6.4 vs. -6.3 mg/dl), low-density lipoprotein cholesterol (+7.0 vs. -4.4 mg/dl) and triglycerides (+15.3 vs. -10.4 mg/dl) and an increase in high-sensitivity C-reactive protein (+1.8 vs. -1.9 mg/l). Both groups experienced decreases in systolic blood pressure (-4.0 vs. -1.3 mmHg) and high-density lipoprotein cholesterol (-3.7 vs. -0.8 mg/dl). Increased weight during migraine treatment is not associated with poor headache treatment outcomes, but is associated with deterioration of CVD risk markers.