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Why do I always feel hungry when I am so overweight?

This question originally appeared on Quora. Answer by Tom Slijkerman, Food Science Expert.

Hunger is a hormonal signal from your body to ultimately guide you to a certain body composition set-point, that your body regards as being the safest for your particular lifestyle history, in order not to die from food shortages (this might not be a contemporary type of danger for most of us anymore, but evolution is not the fastest responding mechanism). This aiming for a certain set-point is called homeostasis, and is found for many other variables within our bodies: body temperature, blood pressure, glucose levels, etc.

So, even if you're overweight, but just a bit under your personal set-point, you'll become and stay hungry more easily. Your DNA's risk management (which is different for everybody) sets the levels of this set-point, and considers the following;

There is risk in not having enough fat mass, to be able to survive a possible hunger season, but there's also risk in having too much fat mass, since it takes extra energy to move around with all these (heavy) energy reserves, when trying to collect your food, which would result in needing more food consumption than strictly necessary. Better to have those extra energy reserves waiting at home, instead of stuck to your body. So, this downside of fat reserves is only present when physically active. When not regularly physically active, the only thing that's left is the upside of the reserves, which makes it an easy choice for your body, to simply hold on to upward weight fluctuations.

There is risk in not having enough muscle tissue to be able to get to your food, but there's also risk in having too much muscle tissue, which has the unfortunate property of burning energy even when not being used (it raises our metabolisms), which would also result in needing to consume more food than necessary.

This set-point is precisely what causes the infamous yo-yo effect. The following two lifestyle variables can potentially raise your fat reserves set-point by the aforementioned risks;

Regularly eating out of sync with your energy expenditure. This includes periods of eating less then needed, which is simply simulating hunger season: the yo-yo effect will help you regain weight for possible future hunger seasons. Periods of eating more then needed. Eating irregularly throughout the day, like high energy spikes by sugars, which can't all be used up at that particular moment, but also eating less throughout the day and eating more in the evening. All these examples make use of your fat reserve system, which is something you should avoid as much as possible.

Not being physically active on a regular basis: this will let your DNA see no downside whatsoever in having fat reserves: there's no extra energy used whether you're sitting around all day weighing 150 pounds or 300 pounds. Compare your extra fat reserves with an extra large fuel tank for your car in a trailer behind it: when just stationary, the extra tank will never be disadvantageous, no matter how large it is, but when regularly driving around with it, the extra fuel reserves itself suddenly use up a lot of extra fuel by it's own sheer weight.

That same inefficiency is what you want to have every day for your body: but that's simply not happening without moving around enough, like the gatherers of old time used to do.

Most obesity is not caused by gluttony, it's caused by sustained irregular eating (fat reserves simply work as a time buffer between the moment of energy intake and usage) combined with an average lack of physical activity. This is why the prevalence of obesity goes up, while total energy intake goes down in many countries: Obesity in Britain: gluttony or sloth?

So for permanent and healthy weight loss it's all about continuously showing your body you're now living a lifestyle in which your fat reserves are useless or your fat reserves create inefficiency.

Point one is realized by eating very frequently and in sync with your energy expenditure throughout your days and your life, and not restricting (nor over-consuming) calories. Simply try to not make use of your fat reserve system, not even temporary during the day, and then filling it up again with supper.

They often say: "use it, or lose it" for muscle mass, because muscles always have this disadvantage of using up precious energy, even when at rest, so your body really needs to be certain you need them, in order to keep them. The same "use it or lose it" actually also applies to your fat reserves, as long as you also remain physically active to also make them energy inefficient as is the standard case with muscle tissue. But since we usually want to lose fat reserves the advantage is rather in: "don't use 'em and you'll lose 'em".

Try to adjust your meal portions (within certain upper and lower limits) to the hunger signals your body gives you. These signals can be subtle during the day, especially with a busy schedule, but learn to listen to them. Try to eat every 2.5 to 3 hours.

For point two you also need to regularly (daily and throughout the day) move around a lot with your fat reserves. This doesn't need to be intensive at all, but it's beneficial. Time is more important than intensity, though.

After some time your body will start to learn that the 1) unused, 2) energy consuming fat reserves are not to your benefit anymore. Your body needs to trust that this lifestyle is permanent, though, to take the risk of losing those handy fat reserves. It will start considering it permanent by noticing you've been living this way continuously for a long time, so it will, in a way, try to predict the future by using this (new) past and adapt your body for that way of living.

Understand why you really need to make use of this synergy, by using both points together: when only eating in sync with your energy expenditure, without peaks or dips, your fat mass will remain unused, but combined with an inactive lifestyle, there's no downside to still holding on to the reserves, since it won't use up any extra energy. On the other hand, when only having an active lifestyle, your fat reserves will use up this extra energy, but when you also prove everyday you're still making lots of use of your fat reserve system, your body won't decide to lose those handy reserves.

Your set-point will never adapt in a gradual manner, so fat losses caused by your consistent healthy lifestyle will often go in sudden spurts, by reduced hunger feelings and increased metabolism for certain periods. This is very similar, but in the opposite direction, to growth spurts with growing children and body builders. Every now and then it could be useful to alternate the intensity, volume and/or type of your physical activity to encourage your body for another change in set-point.

These weight changes aren't prone to the yo-yo effect but are permanent pounds because they are a direct result of following your set-point, instead of fighting it.

It's very well possible you gain some pounds at first, if you've always been struggling under your actual set-point. Most important thing is that this initial gain didn't change your set-point one bit, which should really be your one and only concern. People showing off 'success stories' with fast and large (but temporary) weight losses, will still remain having the same (but unfortunately hidden) set-point.

Dieting is largely ineffective in maintaining initial weight loss as numerous studies suggest the majority of dieters regain all lost weight with 3 to 5 years.

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