Picture the scene – there’s a group of you, enjoying a coffee or a cocktail together, and someone says idly, “I’ve got to lose some weight.” And you all nod, and then that's the end of it.

But what if you decided to do it together?

More and more, all around the country, groups of people are challenging each other to slim down. And it’s working.

Chris, 24, took part in a weight-loss challenge with his buddies at work.

“All the overweight guys in the group put their names on a chart, then they were supposed to weigh in every week and keep each other motivated.” So far Chris is at the top of the chart, having lost 35 pounds, but it’s not all about the competition. “It’s about doing it for yourself,” he says.

This sort of friendly rivalry could offer just the right amount of extra incentive to keep you away from the Oreos. If you know a friend or colleague has stuck to a healthy salad and skim milk all day, it’s much easier to do the same yourself.

So a group of you have decided to drop a couple of sizes, and you’re all fired up about how great it’s going to be when you all get there. At this point, it’s a very good idea to set some ground rules.

First, the weight loss should be done slowly and sustainably. If a diet or weight-loss program offers miraculous results, chances are it’s a claim too good to be true. The safest, most reliable, and healthiest way to lose weight is gradually and by counting calories.

Remember that each person in the group has different needs, and that the competition should reflect this. Try to set individual goals that are roughly similar, so everyone can attain their goal at about the same time.

If you decide to set up a challenge with co-workers, consider taking half your lunch break to go for a power walk or jog, then have a healthy lunch together afterwards. Maybe bring in wholegrain bread, lean meat and salad for (nearly) homemade sandwiches after your exercise session. Not only do you save on calories, but bringing in the makings of a group lunch is a lot cheaper than heading to a deli.

If there are enough people in the group, you could even set up teams, and a challenge within your weight-loss challenge.

Some larger companies sponsor corporate sports teams and challenges, with activities like softball or a charity fun-run. Talk to your supervisor about setting something up - with the reminder that healthy employees make better workers!