Why does our body make us so hungry even if we're overweight?

I’ve been on a diet for the last few weeks and it always amazes me how my body will decide to make me hungry at certain times and not at others. Despite being overweight I’m never hungry in the morning, and can often skip breakfast and get into the mid-late afternoon before I’m really hungry. In the evening my appetite goes nuts, even if I’ve eaten earlier and if I stay up until 12:00PM - 1:00 AM or later it goes absolutely out of it’s mind trying to get me to eat something, even if I’ve already eaten. Which is really weird because your stomach is growling like crazy and pushing you to eat, but if you sit and think about it you had some soup or whatever earlier, and you’re really not starving to death, but your body is very displeased with the level of intake

How does the body gauge what it “should” weigh and how much food is enough?

Your body wants you to eat as much as possible because food has been scarce for most of human history. It wants you to store fat so you can live through the next famine, which probably isn’t going to come where you live.

People aren’t 100% sure yet, which is why there are very few effective medications for obesity. Some of the signaling hormones (PYY, Ghrelin, Leptin) were only discovered 10-15 years ago.

Your body knows what it should weigh based on a variety of signals and factors all relating together coming from various areas (the stomach, intestines, fat cells, etc). Plus some of the signals are redundant, which is why using one medication to lose weight usually doesn’t work too well long term. People can lose weight with catecholamine drugs like phentermine, but the weight usually comes back. We’ve evolved not to starve to death, so the system of homeostatis is probably pretty redundant.

I barely understand it, but I know its pretty complex. But what your body thinks you should weigh (based on the chemical signals being sent back and forth) and what society thinks you should weigh aren’t the same thing 99% of the time. And your body is going to win in the long run.

That certainly has something to do with it, but something varies from person to person. I’ve never really been overweight, despite not making much of an effort to eat well or exercise for most of my life. But other people struggle with their weight for their entire lives. My sister (so more or less the same genes) has had issues with her weight since she was little.

When hunger is triggered, the body is generally NOT looking at its total stores. As a matter of fact, long-term starvation has an associated mechanism that diminishes hunger.

There are triggers for hunger and satiety, and these are not directly related to how fat you are. As mentioned above, the triggers and feedback loops are quite complicated, and layered upon physical anatomy as well. As an example, we could give a guy a tiny stomach surgically, triggering a much earlier satiety because his stomach gets full so fast…

Rather than dig into the chemical pathways that are understood poorly anyway, let me use a metaphor:

Immediately available energy (simple sugars like glucose) is cash.
Short-term storage (glycogen, say) is a checking account.
Long-term storage (fat, say) is a retirement account.

When you get low on cash, your body wants to eat, even if you’ve got a few million stored in your IRA. When the cash is low, it will transfer energy from your checking but use your fat IRA only as a last resort after exhausting all other efforts.

It is for this reason that many weight loss programs recommend adjusting your eating styles and times as well as absolute quantities and specific foods. Essentially the whole argument over what’s best boils down to better satiety as well as just controlling calories. Controlling calories alone is very hard to do because hunger is such a powerful drive.

From an evolutionary perspective (and hence why we are the way we are) there is almost no one who died because they were too well fed, but lots and lots of people who have died because they didn’t have the energy reserves to withstand a period of low food. The idea of eating ourselves to death is a very modern phoenominon from a biological perspective, and generally it does not cause significant (ie procreation-preventing) problems until quite a while after humans start procreating. IOW, there’s no reason for a mechanism for the body to monitor its weight and strive for what we would in modern times consider ideal because there was no real advantage to it.

I am no expert, but I always thought it would be interesting to clinically study people who never seem to gain extra weight. We all know someone who can eat as much as they want, as often as they want, and remain skinny. Assuming that they aren’t anorexic or bulimic, how are they biochemically different from the rest of us?

Something about their metabolism is either burning up all of the calories they take in extremely efficiently, or it doesn’t allow fat to be stored like the rest of us. While some of these people appear hyper-metabolic, e.g. hyperactive, others seem just as sedentary as I am. So what is it about the way they are genetically programmed that allows them to burn so many more calories a day than I do. If metabolic rate in humans falls on a bell curve, these people are clearly outliers.

While this kind of hyper-metabolism may have worked against them in the stone age, it seems they are now more likely to survive, and presumably reproduce more, than the average person who at 30-50 pounds overweight is a heart attack waiting to happen. Do these skinny people have any adverse health issues associated with low weight or are they less likely to have a heart attack or get cancer than the average person?

In the future we may be able to “tune” our genes to keep us at the perfect BMI weight for our height. Wouldn’t that be nice…

IIRC, even when exercising, your body will exhaust all of its sugar reserves and other easier sources of energy before it starts metabolizing fat.

which dovetails nicely into why you’ll get hungry even if you have much fat stores - your body wants the easy way out. it’s a lot less work for your body to metabolize simple sugars than it is to start chewing its own fat.

IIRC, one poster has a mother who is that way – apparently she has a congenital disorder that prevents her from storing lipids and cholesterol effectively. She’s skinny but with super high cholesterol.

but I think much of it is just perception. there’s a reality show somewhere (UK, I think) where they dig up a superskinny guy who claims he can eat whatever, and they dig up a heavy guy who claims he diets and diets but never loses. They switch the diets of these 2 guys, and inevitably, the skinny guy gains weight, and the heavy one loses weight.

All I know is that despite a regular running regime, I only start to lose weight when I’m training for long events, and doing runs that are eight miles or longer regularly. When I’m not training for long-distance events, my normal run is between three and six miles four or five times a week, and I’ve never lost any weight then (I don’t gain any, either, though). But once I start a weekly 8-15 mile run, the pounds come off like nobody’s business.

I’ve had several experiences with weight losss that were eye-opening to me. I have always been a little overweight – anywhere from 10 pounds to 185 pounds overweight.

When I weighed around 250, I was put on a liquid diet of about 475 calories a day and remained on nothing but liquids for six months. It was tiresome at first, but after a while, I got used to it. Then I began to forget meals because I just didn’t think about eating. I wasn’t hungry at all. (This fits in with what Chief Pedant says about starvation and not being hungry.) I had gone from being a compulsive eater to forgetting to eat. About three days after I had to start eating regular food, I began to crave sugar and starches. I could not control the impulse to eat them anymore than I could control breathing. I gained all of the weight I had lost back.

After a gastric by-pass at 300 pounds, I began to gain some of the weight back. I got full very quickly, but I was still feeling the compulsion to eat all the time too. A medication took care of that, but I had to keep increasing the medication.

Now I’ve switched to another medication and once again I’m not interested in eating.

For me, much of eating has to do with brain chemistry. And I would add to that that I may have an addiction to sugar also. But it is not a matter of will power. I proved my will power by drinking nothing but liquids for six months.

Also, a full or empty feeling stomach has nothing to do with weight. It has to do with how much you have or have not eaten, right?

The reality is you (and I and everyone on this thread) is one of the outliers if you look at the extremes. I don’t think any of us could ever be 550 pounds, no matter how hard we tried. But there are people who weigh 550 pounds just by following their innate biological urges (which everyone follows). Just as you feel an extremely skinny person is an outlier with an advanced metabolism, a person who naturally weighs 600 pounds feels the same way about you.

I think part of it has to do with the creation of new fat cells. I think some people just have a small number of adipose cells, and their bodies do not create new ones. So when they gain weight, their fat cells become stuffed too much (rather than new ones being created to store the excess) which causes their hormonal system to change which results in lower appetite and more energy until the excess fat is destroyed.

The future of obesity treatment might be closer to cancer therapy, since it will be the intentional targeting of certain cells for death (in this case adipose cells) while leaving nearby cells healthy.

Being 30-50 pounds overweight isn’t necessarily a heart attack waiting to happen though. Being obese can increase CVD risk by 50% or so, but there are dozens of risk factors and interventions that can be looked at to lower risk. The rates have been declining.


Decline in CVD Death Rates

Age-adjusted death rates per 100,000 persons (standardized to the 1940 U.S. population) for diseases of the heart (i.e., coronary heart disease, hypertensive heart disease, and rheumatic heart disease) have decreased from a peak of 307.4 in 1950 to 134.6 in 1996, an overall decline of 56% (1) (Figure 1). Age-adjusted death rates for coronary heart disease (the major form of CVD contributing to mortality) continued to increase into the 1960s, then declined. In 1996, 621,000 fewer deaths occurred from coronary heart disease than would have been expected had the rate remained at its 1963 peak (1).

Age-adjusted death rates for stroke have declined steadily since the beginning of the century. Since 1950, stroke rates have declined 70%, from 88.8 in 1950 to 26.5 in 1996. Total age-adjusted CVD death rates have declined 60% since 1950 and accounted for approximately 73% of the decline in all causes of deaths during the same period (1).

People are getting fatter and fatter, but it is not an X=Y proposition between obesity and heart disease since heart disease involves tons of risk factors and interventions. The death rates of CVD have declined in sync with our obesity explosion.

Here is a list of 30 ways to take better care of your cardiovascular system.


Personally no, I don’t think so. Once we have the biotechnology to purge all social deviance from our minds and bodies, what will we be at the end of the day?

I can understand the urge to not be fat in a society that equates being fat with being sexually unattractive or socially stigmatized, but what happens when we actually know how to get rid of every deviance? No more crooked noses, no more love handles, no more acne scars. Its going to be a world where people feel their worth, identity and value does not extend beyond their capacity for social standing.

Anyway, I’m not condemning weight loss. I’m just saying that a world where we have the tools to eliminate everything about us that makes us (or makes us feel we are) sexually unattractive or socially deviant is going to have negatives associated with it too.

Most people have never actually felt true hunger. Also hunger will go away once you get used to. Anorexics can not eat so easily 'cause they get used to it.

For instance when I’ve got on 48 hour water fasts, the first day you feel worse than the second day, 'cause your body has adjusted.

Your body always takes the line of least resistance. What happens is you don’t eat and after around 24 hours you start to feel hungry and your stomach gets signals, saying “It’s time to eat.” You see it’s much more efficient for the body to take in new carbs (which are fast food, in a way) than to use the fat on your body.

This is the discomfort, but it’s not actual hunger pains. I would say it’s more akin to, for lack of a better word “hunger pangs” which is a desire to eat. If you continue to ignore your body’s demands for food. The body then says "OK something’s up. We better start to use the fat. And gradually the body uses the stored fat as energy.

But the body doesn’t do this till it is sure. In other words you body has to say “OK this guy isn’t gonna eat so we have to do something.”

Now fat has 9 calories per gram, compared to 4 calories for carbs and protein. So by the second day of a fast, your body has started releasing this fat for use as fuel. And because fat has more than twice the energy, people actually feel better the second day of the fast. Because you’re getting more energy.

But again your body isn’t going to just use fat. It is programmed to use fat as a last resort or when it’s more efficent to use fat than carbs. So around the third day the body starts producing actual pains telling you to get your butt in gear and look for food.

If you don’t eat then the body once again, will start to use the fat.

This is why an average person with no health issues can live about a month (more or less) without food. Of course you need water during this time. And if you have health issues like diabetes or other metobolic problems you won’t last that long.

So remember your body takes the line of least resistance. It’s made to put the fat on and only use it when the body decides it’s absolutely necessary. And it’s not uncommon not to eat. There are places in Africa where it’s common to eat only three or four times a week. These people are healthy, but the body has gotten use to it.

[QUOTE/ How does the body gauge what it “should” weigh and how much food is enough?[/QUOTE]

Not so much the body but the brain… After I go to the grocery store, my consumption skyrockets given the number and variety of treats just a few yards away.