Research suggests that roughly 80% of people who shed a significant portion of their body fat will not maintain that lost weight for 12 months.

One meta-analysis of intervention studies also showed that, on average, dieters regain more than half of what they lose within two years.

So, what’s behind this frustrating rebound weight gain? Putting back all the weight you lost (and more!) has become synonymous with restrictive dieting approaches.

These unfavourable outcomes typically lead to yo-yo dieting as people simply perpetuate the cycle in an attempt to lose the weight they regained. But the outcome seldom, if ever, differs.

Real-world evidence

Research out of UCLA confirms that dieting is a consistent predictor of weight gain. Up to two-thirds of people included in 31 long-term studies reviewed as part of a meta-analysis regained more weight than they lost.

A mere 5% of people who lose weight on a crash diet will keep the weight off, according to data from Stanford University.

To further illustrate this propensity to regain weight after a diet, a 2011 study conducted on over 2,000 sets of twins from Finland showed that the twin who embarked on just one intentional weight loss episode was two to three times more likely to become overweight, compared to their non-dieting sibling.

Furthermore, the risk of becoming overweight increased in a dose-dependent manner with each diet. The study results indicate that dieting itself, independent of genetics, is significantly associated with an increased risk for weight gain.

Researchers concluded that “the more people engage in dieting, the more they gain weight in the long-term.”

READ MORE | Experiencing Unexplained Weight Gain? Here Are 5 Possible Reasons

More than mental

The biggest reasons that many people regain weight after a diet is their failure to change their lifestyle habits.

Severe calorie restriction is also unsustainable and produces diminishing returns the longer you stay in a calorie deficit.

Furthermore, physiological changes occur after weight loss that drive your desire to eat and regain weight, including changes in appetite-regulating hormones like ghrelin and leptin.

Consequently, significant weight loss makes it harder to resist calorific or high-carb foods and overeat. And the more people diet, the stronger these impulses tend to become.

This basically means that the process of dieting itself increases your body’s propensity to gain weight, a response that scientists have termed “dieting-induced weight-gain”.

Hunger is an extremely powerful impulse as it is hardwired into our subconscious as a survival mechanism. While various psychological reasons trigger the impulse to eat, the hunger we experience after restrictive dieting serves a specific physiological purpose, as demonstrated in numerous studies.

READ MORE | Does The 500-Calorie-A-Day Deficit Rule Work For Fat Loss

Weight homeostasis

At its most basic biological level, your brain interprets the dieting process as starvation. It will therefore initiate processes that place your body in ‘survival mode’.

Subsequently, your metabolism slows and you experience food cravings, which serve as important physiological processes aimed at survival.

A landmark study published in the Journal of Advanced Nursing Practice in 2013 looked at “promoting homeostasis (a state of equilibrium or balance) to avoid rebound weight gain in yo-yo dieters”.

The study uncovered “a host of orexigenic (appetite-stimulating) and anorexigenic (appetite-suppressing) hormones working to keep a stable healthy weight”.

This basically means that, when we deplete stored energy – glycogen, body fat and, to a lesser extent, muscle – through dieting, we experience a compensatory effect to replenish these lost stores. This process is characterised by intense hunger and overeating.

The study also highlighted other compensatory mechanisms that lead to rebound weight gain, including involuntary responses to hunger that lower metabolism, reduce thyroid hormone production, and increased fat cell production.

This led researchers to state in their paper that “weight homeostasis resists weight loss, not willpower”.

They also explained that weight homeostasis is a process that aims to “err on the side of resisting ‘starvation’ over the promotion of weight loss … when calories are withheld to the point of hunger, the body becomes flooded with hunger hormones. The hungry individual is spurred to eat, and thus eats a lot. Eating in response to hunger is a voluntary way to replenish lost energy stores.”

READ MORE | 5 Signs You Have A Bad Relationship With Food

Hunger hormones

Our primary hunger-stimulating hormone is ghrelin. When you restrict food intake or rapidly lose weight, your body secretes more ghrelin. In addition, leptin production decreases, which is the hormone that signals satiety.

In an effort to prompt higher food intakes during and after a diet, your body develops a tolerance to appetite-suppressing hormones over time, but we never develop a tolerance to appetite-stimulating hormones.

As a result, these hormones can stimulate feelings of hunger indefinitely.

A study published in the New England Journal of Medicine found that these hormone levels can remain altered for up to 12 months after a diet. This chronically altered hormonal state makes it extremely difficult to resist the urge to eat to maintain your post-diet weight and body composition.

READ MORE | Why Your Food Bill Increases In Proportion To The Intensity & Volume Of Your Training

Metabolic slowdown

And in an effort to preserve energy stores, your body will also down-regulate your metabolism. Studies conducted at Columbia University show that the associated metabolic slowdown means people must eat around 400 fewer calories a day after a diet than they did before starting it.

Your body also becomes more fuel-efficient following periods of calorie restriction – studies indicate that muscle fibres in dieters burn up to 25% fewer calories during exercise than those found in a person who maintained their weight.

READ MORE | Calories And Kilojoules: Know The Difference, It’s Important!

A losing battle?

All of these processes work together to tell your brain you’re hungry and ensure that you don’t stop eating until you have regained the lost weight, and then some. Technically, the body works to resist weight loss as much as possible, while prompting weight gain.

The good news is that you can prevent rebound weight gain. You first need to establish a new sustainable lifestyle that includes healthful eating habits and regular exercise, then reprogramme the way you think about food.

Increasing your protein intake may help. A study published in the American Journal of Clinical Nutrition showed that participants who ate a high-protein diet and used portion-controlled meal replacement supplements were less likely to experience rebound weight gain.

Researchers attributed this effect to the increased satiety that high-protein meals create, along with a modest increase in energy expenditure.

Most importantly, avoid overly restrictive diets or excessive exercise – they are generally unhealthy and unsustainable methods to lose weight and keep it off.