Did you know that a rats favourite treat is a chocolate milkshake? It’s true. You wouldn’t expect a rat to have a problem with obesity, or to be a picky eater, but both of these assumptions would be wrong. Offer them a strawberry or vanilla milkshake and they turn their nose up, but give them a chocolate one and they fill their furry little boots. So much so that if they eat a diet entirely made up of chocolate milkshakes they double their weight in ten weeks but put them back on a normal rat diet and their weight goes straight back down again. A rats’ weight, like ours, seems to be determined by its lifestyle.
This concept of yo-yo dieting has often been attributed to the existence of a so-called, body fat setpoint. The idea is that the body has an innate, genetic, fat percentage that it will always try to return to, regardless of how much weight you lose. This concept isn’t new, and it’s vocally supported by science-savvy nutritionists and normal folks alike. Belief in this genetic level of body fat can lead to sayings such as “I’m just built this way” or “I might as well not bother, I’m only going to get fat again anyway”. Neither of which are particularly liberating thoughts.
However, like our, milkshake loving, rat friends, a pre-determined level of body fat might have less to do with our genetics, and more to do with our choices. Metabolisms can slow during weight loss, and you might be more hungry than normal after shedding the pounds, but with careful planning and decent food choices, you in no way doomed to be bigger than you’d like because your genetics say so. There is no body fat setpoint.
A thermostat works to maintain the temperature. If the temp drops, its sensors will pick it up and add some heat. If it hots up too much it’ll do its best to cool things down. This closed-loop control system is what gives your hotel room a nice, fixed, climate. Your body maintains tonnes of internal conditions in exactly the same way. Your body fat percentage, however, is not one of them.
It’s true that some people may be at a greater risk of obesity, and that a lot of this risk is to do with genetics, but it isn’t a foregone conclusion that you are doomed to be overweight just because your genes make it easy.
- A study by Bouchard looked at the effect of genetics on overfeeding by giving sets of twins an extra 1,000 calories a day over their maintenance.
- The amount of weight that people gained was hugely different, ranging from 9 to 30 pounds.
- What makes this study so interesting is that each set of twins, having identical genetics, gained the same amount of weight.
- This points to genetics as having a huge impact on how much weight we are likely to put on, with some lucky folk in the study getting away with only putting on a small amount while others ended up gaining more than three times as much.
However, the point that most people miss in this study is that the weight gain wasn’t inevitable. It only happened because these people were made to eat 1,000 calories more than normal each day.
Your genetics do make a difference in how you store fat and how easy it can be to gain it, but they do not predispose you to being a certain weight, regardless of if you’ve been on a diet and lost fat or not. Only your lifestyle does that, and that’s within your control.
“The biggest loser” was a reality TV show where people competed to lose the most weight within a set time. People lost astonishing amounts, but most of them gained it all back after the show was finished. As well as the press having a field day at their expense, the scientific community picked up on it too.
While we know that your body adapts to weight loss by slowing certain processes down to conserve energy, researchers found that even 6 years after the show, the contestants’ metabolisms were still lowered more than should be expected. This led people to believe that their fat re-gain was the set-point at work, quietly driving them back to the weight they were before. But reading the paper a bit more closely points to the opposite as being true. Two things stand out.
- Metabolic adaptation isn’t a one-way street. While your body slows things down when energy is restricted, it also makes fat gain harder by speeding things up when someone eats more calories. An often missed quote in the study actually pointed this out by stating “Weight regain was not significantly correlated with metabolic adaptation at the competition’s end”.
- All of the competitors lost muscle and didn’t put what they had lost back on again after the show. As fat burns far fewer calories than lean mass, the overall slowing of metabolism could be a problem if you only do cardio and forget to lift weights during a diet.
If you’ve ever bumped into someone you used to know years later and noticed how they are way leaner than when you knew them, you should know that the set point theory is a myth. Lifestyle matters and genetics aren’t destiny.
You can change your weight forever, as long as you change your lifestyle too. This is a good thing because while permanent change can be hard, it’s you who ultimately has control over your weight and health. There is no body fat setpoint.