He also taught for long spells at Maastricht University and the University of Tilburg.
Satisfaction with life starts to drop as early as a person's late 20s and does not begin to recover until well past 50, says Bert van Landeghem, an economist at Maastricht University in Belgium.
In one of the new studies, researchers at Maastricht University Medical Center, in the Netherlands, examined 24 young men, about half of them lean and half overweight.