If you’ve ever lost weight only to find that over time you regain every kilo, you’re not alone. The discouraging fact is that as many as 95 per cent of women and men who escape obesity eventually find themselves heavy again. Dieting, plain and simple, doesn’t seem to work. That’s because it’s not just our physical health that’s at stake but our mental health, too. Anyone whose weight has ever yo-yoed knows that the regained kilos are nearly always accompanied by an unhealthy serving of self-loathing. “People feel guilty when they gain the weight back, like it was a personal failing,” says endocrinologist Dr Scott Isaacs.

By you shouldn’t be so quick to judge yourself. According to Isaacs, the weight regain is not simply a matter of failed willpower − you’re battling biology. In fact, ongoing research has determined three powerful physiological changes that work side by side to drive your body to pack the kilos back on. While that’s frustrating news if you’re trying to lose weight, keep in mind that knowing what you’re up against is half the battle. So instead of giving up or thinking negative thoughts, keep reading and then you can pair your new understanding with these science-backed tactics. They’ll help you tackle the biological hurdles, and finally outsmart your metabolism and the dreaded yo-yo for good.


Along with your eye and hair colour, your parents passed on other genetic characteristics. Increasingly, experts believe that one of them is a so-called set point − a general weight at which your body feels comfortable. While it is largely determined by genetics, which explains why some people struggle with gaining weight just as much as others struggle with losing it, scientists now believe that your set point can change throughout your life. Each time you put on weight, your body gets comfortable with your newfound bulk. Clueless to the fact that modern society is blessed with an abundance of food, your ‘just in case’ genes want to keep the extra body fat stockpiled for the famine that may be lurking around the corner. Basically, if you struggle with keeping weight off, part of the problem may be your genetic inheritance. After all, for most of human history, food was scarce. Your ancestors survived only because they hung onto enough extra weight to avoid starving to death. Then they passed their thrifty genes on to you, says weight-loss specialist Dr Caroline Cederquist. So how does your body know how much it has in reserve? The set point is largely governed by a part of the brain called the hypothalamus. By reading the signals fat cells send, your hypothalamus gauges whether you have enough extra resources to outlive a sudden food shortage.

“Our genetic predispositions haven’t kept up with our environmental shifts,” Isaacs says. In short, they don’t take account of the fact that food is available 24/7 in our modern world. “Our bodies still aim to prepare us for tough times ahead.” Biologically, your body has a few ways to try to preserve a new, heavier set point. One is by reducing the amount of energy it expends to stay alive. Just as you would adjust the thermostat to create the ideal room temperature, your body turns down the burn on your metabolism − and not just by a little. In a landmark study, researchers followed the lives of contestants on the US version of The Biggest Loser after the cameras had stopped rolling. In the heat of the spotlight, they had lost an average of 59kg. But six years after the study, almost all of them had regained an average of 41kg.

Moreover, researchers calculated that the participants’ resting metabolic rates − the amount they burn in a day without additional exercise − had slowed drastically. Six years after being on the show, each contestant was burning an average of 2,000 fewer kilojoules per day than would be expected of a person of similar size.

Even less-extreme weight-loss programs can drive metabolisms to a lazier crawl. According to one US study, people who’d lost a more modest 10 per cent of their body weight burned about 600 fewer kilojoules at rest than would be expected, and these changes persisted for as long as six years. So even when you lose just a few kilos, biology works to drag your body back up to its set point or to a new, higher one.


Does that mean biology really is destiny? Well, you can’t change your genetic heritage, but there are steps you can take to speed up your
metabolism. Maintaining lean muscle mass as you lose weight gives you the best shot at burning as many kilojoules as possible throughout the day, since muscle tissue burns more kilojoules than fat tissue. Experts advise starting a total-body strength-training program and building up to two or three resistance workouts a week. (Don’t forget to squeeze in a cardio workout, which plays a big role in weight-loss maintenance, as well.) You can also encourage muscle building by eating plenty of lean protein, which provides your body with amino acids, the raw materials for making metabolism-revving muscle tissue. While the recommended daily intake of protein for the average woman is around 50g to 70g, some experts believe that a higher protein intake (100g to 120g) while losing weight is essential, so your body doesn’t lose lean tissue and cause your metabolic rate to drop. To keep your body in muscle-building mode, Cederquist recommends evenly dividing your protein intake throughout the day. Ideally, you should aim for three proteinrich meals of about 30g each(a 100g chicken breast, for example, has 30g of protein) and several snacks with about 10g each (such as 40g of hard cheese or ¼ cup of tofu).


The hormones that regulate how hungry or full you feel can step in when you start to shed weight. In the Biggest Loser study, scientists found that the blood levels of the appetite-suppressing hormone leptin in participants dropped 93 per cent – that is, to almost nothing − immediately after they left the show. Since leptin is the hormone that signals when we’re full, lower levels of it mean the body doesn’t receive the message to put the fork down. The leptin levels of Biggest Loser participants did rebound over six years, but only by two-thirds, so the participants continued to feel like they were starving, even after they’d met their daily kilojoule needs.

Unfortunately, it is not just a problem for TV weight-loss contestants − a landmark study published a few years earlier in The New England Journal of Medicine confirmed that a flux in hormones could cause dieters to suffer from a ravenous appetite as the kilos fell away. Researchers followed 50 people who each shed about 14kg over 10 weeks on a medically supervised liquid and vegetable diet. A year later, they had regained an average of 5.5kg and had leptin levels 35 per cent lower than when they had started.

In the study, blood samples also revealed changes in other fullness-signalling brain chemicals, including amylin, peptide YY and glucagon-like peptide 1, or GLP-1. The levels of nearly all these hormones fell off as the kilos did and never rebounded. Meanwhile, levels of ghrelin, the hormone that increases appetite, surged right after weight loss, then dropped slightly, and finally settled at a higher level than they had been before the weight loss.

If you’ve gone through yo-yo weight changes more than once − especially if your regain was fuelled by junky carbs and fatty treats − your body may not be as quick to respond to hunger-satiating hormones. Research indicates that years of unhealthy eating can cause the body to develop a resistance to the remaining amounts of these hormones. That’s because foods rich in low-quality carbohydrates and saturated fat create inflammation that injures neurons in the brain. As a result, the neurons can no longer read the signals that hormones like leptin send, making you feel even hungrier, according to a recent article in the British Journal of Nutrition. And while losing weight reduces the inflammatory processes and helps repair the sensors, shedding kilos alone may not counter all the damage that has been done.


While researchers look for medical solutions to manipulating those hunger-hormone levels, there are a few steps you can take by yourself to help tweak the system. For one thing, make sure you get enough sleep every night, since sleep deprivation makes the problem worse by further lowering levels of hunger-satisfying leptin and upping levels of hunger-stoking ghrelin. A lack of sleep also tempts you to make unhealthy food choices. In a recent study, people restricted to four and a half hours of sleep for four days consumed about 1,600 extra kilojoules in snacks, compared with when they were able to sleep for a solid eight hours.

Dietary changes can help outsmart hunger hormones, too. Replacing simple carbs, like pasta and white bread, with low-kilojoule foods that are rich in water and nutrients, such as vegetables, can help combat a growling stomach. One year-long study found that people who ate the same number of kilojoules but double the amount of vegetables felt significantly less hungry. Why? Your plate looks full, your stomach expands, and it takes you a while to munch your way through the food. Adding in low-kilojoule, but filling, foods like water-rich vegetables doesn’t provoke the same spike in hunger-inducing hormones or the drop in fullness signals that typically occur following weight loss. Avoiding high-fat foods may also keep hunger hormones in check, since these can further disrupt the system from signalling satiety at the right time.

Finally, studies have shown that a diet rich in protein and fibre can regulate ghrelin and decrease appetite.


Now you know the way biology turns your body against you in the fight to stay slim, can’t you trust your self-control to rise above these urges? Not easily, unfortunately. Weight loss also produces changes in the brain that may make it harder to resist the siren song of cake and chocolate. Research shows that reward pathways, similar to those that drive us to have sex, take drugs and gamble, light up brightly when, after shedding kilos, we’re faced with a tempting treat.

One study scanned the brains of hungry dieters as they ogled photos of appetising food, both before and after a 12-week weight-loss program. After they’d shed kilos, dieters showed greater activation in part of the self-control system called the medial prefrontal cortex, which governs attention and focus. “We can translate that to mean food has become even more important than before they lost the weight,” says study author and medical researcher Amanda Bruce.

You could call it a neurological double whammy: you’re more focused on, and motivated by, food and, at the same time, the unhealthiest food choices appear appealing.


To counteract these brain-directed urges, experts suggest you try providing yourself with alternative rewards. Weight loss feeds the brain with a steady supply of positive reinforcement: compliments, looser clothes, smaller numbers on the scale. But all these evaporate once you reach your weight goal, making the brain-pleasing allure of fatty, high kilojoule foods harder to resist, Bruce says. Replace these mini-highs with non-food sources of positive reinforcement, such as small monetary or shopping rewards, for sticking to your goals. This can send brain signals down similar reward pathways to those that drive you to seek food, making you less tempted to reach for dessert.

Another way to boost your pleasure is to combine a small amount of the high-kilojoule dishes you crave with a heaped helping of leafy greens or other nutritious items. This approach, called the vice-virtue bundle, cuts down the kilojoule count but still satisfies, a study published last year shows. If you aim for a ratio of 75 per cent wholesome and 25 per cent indulgent at each meal, you’ll tame cravings without issuing those extra kilos a return invitation, Isaacs says.

© Prevention Australia