Dieters who have lost a significant amount of weight but regain the pounds soon after, aren't slipping into old eating habits - they're just giving into the demands of their hormones, according to recent research.
The study shows that key hormones drive the body's urge to eat and make it yearn for more food up to a year following weight-loss, leaving the dieter too weak to resist.
The Australian study, published in the New England Journal of Medicine, enrolled 50 overweight and obese volunteers on a 10-week diet program. The aim of the study was to focus on those who managed to lose 10% of their body weight.
Out of the volunteers, 34 lost the weight required. The successful dieters were then put on a strict meal replacement plan where they consumed 500 to 550 calories a day for two weeks, and were reintroduced to ordinary foods soon after.
The researchers found that despite the dieters being given plenty counselling and dietary advice on how to maintain their new, healthy weight, all of them regained an average of 12lbs over the next year.
To find out why this happened, researchers checked the blood levels of nine different hormones that have an influence on the appetite and compared these to the hormone levels recorded before the weight-loss occurred.
They discovered that six hormones out of nine were out of balance following the weight loss, meaning their hunger levels had rapidly increased.
So why does the body, which has managed to shift weight to begin with, resist further weight-loss and give in to hunger?
"It's an evolutionary holdover from earlier times, when weight loss could threaten survival and reproduction," Dr Rudolph Leibel, an obesity expert at Columbia University in New York, told the Daily Mail.
"It's not surprising that our bodies would fight back for at least a year. This is probably a more or less permanent response. People who lose significant weight not only gain a bigger appetite but also burn fewer calories than normal, creating a perfect storm for weight regain," Dr.Leibel added.
Can we really blame our hormones for gaining weight or is it yet another excuse to add to the pile?
If you're struggling with weight-loss, take a look at our expert tips on how to lose weight - the healthy way.