Depression can make you fat but being fat does not necessarily make you depressed. Researchers from the University of Alabama used data from the Coronary Artery Risk Development in Young Adults study, a long-term study of 5,115 men and women aged between 18 and 30 who were followed over 20 years. At five-year intervals the participants were weighed, had their waist-hip ratios measured and were asked about their mood. Everyone gained weight over the course of the study but those who started the study feeling depressed increased in abdominal obesity and BMI at a faster rate. After five years their waist was, on average, 1.5cm thicker and by year 20 it was 2.6cm higher. However, a high initial BMI and waist circumference did not influence the rate of change in symptoms of depression over time. Reports have shown that cortisol - a hormone linked to stress - is also related to depression and abdominal obesity so this could be the link.
You can find out more about this research at