Almost everyone who has tried to lose weight has tasted the bitter pill of failure. That feeling you get when, despite all your desires to be healthier, to fit into sassier clothes or to shimmy through life (and into aeroplane seats) with greater ease and comfort, you just can’t stick with your diet and exercise plans for long enough to get there.
People failing to lose weight frequently blame themselves, as does almost everyone around them. In fact, even a sizeable proportion of health professionals consider obesity to be an individual failing. But this attitude displays complete ignorance of human physiology and how it impacts weight loss.
Fighting famines, not winning weight wars
In actual fact, most diets fail because the body activates a series of powerful physiological mechanisms – many originating fromchanges in the hypothalamus, which lies at the base of the brain – that help to protect us from losing too much weight too quickly.
These mechanisms, which I call the famine reaction, have been pivotal to our survival as a species because they prevent ongoing weight loss and promote weight regain. In pre-agricultural times, which forms the majority of human history, food supply was much more dependent on seasons and intermittent. Conserving energy ensured survival through the lean season.
But while the famine reaction undoubtedly helped the species survive recurring famines and hardships, it presents an enormous challenge in modern societies where the abundance of food (especially energy-dense food) means many people are now overweight or obese.
The famine reaction is a whole-of-body response to not getting enough food with three main symptoms.
- Hunger – when you start a weight-loss program, you might not feel very hungry at all. But once you lose a certain amount of weight, you can eat your whole day’s diet ration and still feel hungry … and it’s only 10.30 in the morning.
That’s the famine reaction pushing you to eat more and help protect you from losing any more fat.
- Lethargy – keeping active can be a challenge at the best of times, but when you’ve lost weight and your famine reaction has been activated, you can feel like you’re dragging your whole body in mud just to get through the day.
You’re being slowed down so you don’t waste precious energy and lose any more fat.
- Feeling cold and shivery, even in the middle of summer – this is your famine reaction reducing your metabolic rate. The result is that weight loss can come to a complete standstill (or plateau), even if you’re still sticking rigorously to your diet and exercise plan.
These effects are incredibly powerful, and help explain why most people hit a plateau and gain back some or all of their lost weight shockingly quickly.
Health-care professionals, the weight-loss industry and members of the public alike assume the energy-conserving effects of the famine reaction are only felt by lean people after extensive or rapid weight-loss (because they need to be protected from wasting away).
But this adaptation has been shown to happen even in overweight and obese people after loss of as little as 6% to 12% of body weight. And even in cases when weight loss has resulted from moderate energy restriction, with or without physical activity.
Fighting the famine reaction
If you listen to standard advice from the majority of weight-loss programs, you’ll think the famine reaction and its secret weapon, hunger, will just go away with judicious use of willpower.
All you have to do in the meanwhile is ignore how hungry you’re feeling, or try to quash your hunger by filling up with non-starchy vegetables, which are part of the “free list” in most diets because their low calorie and carbohydrate count means you can eat as many of them as you like.
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