Professor Mark Conner of the Institute of Psychological Science at the University of Leeds said a "buddy system" could make a big difference to people following dieting plans or other health programs.
"Specific plans regarding when, where and how a person will act have been termed 'implementation intentions,'" Conner said in a statement. "We already know that these kinds of plans can be really effective. You set up cues that prompt your planned behavior -- 'if I walk to work on Monday, then I will jog home,' 'if I feel hungry before lunch then I will eat an apple, not a chocolate bar.'"
Conner and colleagues Dr. Andrew Prestwich and Dr. Rebecca Lawton, also of the University of Leeds, demonstrated this effect can be made even stronger by getting friends, family or colleagues involved.
The researchers worked with employees from 15 places who volunteered to participate in two studies attempting to increase their levels of exercise or improve their diet.
Some employees were left to do it on their own, others were asked to recruit a partner, a third group were encouraged to develop "if ... then" plans, and a fourth group was told to make the 'if ... then' plans with a partner.
The researchers checked on the study participants at intervals of one, three and six months.
"It was clear working together and joint planning really helped employees stick to their new exercise regimes," Conner said.