Very misleading article. The vast majority of human obesity is not caused by genetics - indeed, this is why we have many more obese people now than we did a century, although we have the same genetics. Our great grandparents gave their genes to us, but they didn't suffer as much from obesity because they ate only what they needed and were more active.
For the unfortunate minority that truly does have a very strong genetic component, the fact remains that eating slightly less - just 10-15% less, will allow them to match their metabolism.
This is not to say we should "blame" people - social and environmental factors are very important. Lack of sleep due to too much work / artificially lit environment causes more eating, lots of food is engineered to be super tasty for us, there were no cookie trees in our ancient past :)
Calories per capita per day is up from 2168 in 1970 to 2673 in 2008. If you're at maintenance weight, that extra 500 calories per day will cause you to gain about a pound a week until you reach equilibrium again ~50 pounds heavier.
Sure, caloric intake is up. But we don't know whether calories per capita per day increasing is a cause, an effect, or both. Maybe all it means is that something changed to make people hungrier than they were before. For instance, there's the "fat virus". It's possible that obesity is literally contagious and more people caught it with, say, the growth of air travel.
But what if genetics hasn't changed? I honestly don't know, and it certainly looks like the first world diet has gotten higher in calories and that people in the first world have gotten more sedentary—but, what if it's another factor? Epigenetics is a possibility but there are others as well.
Another major difference is antibiotic intake. I don't know if humans consume enough antibiotics to affect their weight, but antibiotics are regularly administered to livestock primarily to fatten them up. We're just scratching the surface of the human biome and it's entirely possible that there's an answer in there.
You might be right (and my intuition agrees with you) but I wouldn't be so certain of it. Life is incredibly complex.
Life is definitely complex, but most of the variables with some influence on weight are either unobservable or unchangeable.
Luckily, you don't need to observe them or change them. You can ignore them and focus on what is observable -- appearance and weight -- and on what is controllable -- diet and exercise.
It may well be that gut biomes, antibiotic usage, inflammation, corn syrup, global warming, diesel particulates, preservatives etc etc have an influence. But the forcing factor in the weight system is net caloric balance, which is also the easiest to control.
> But the forcing factor in the weight system is net caloric balance, which is also the easiest to control.
Are you kidding? Almost nobody who diets to lose weight manages to keep it off for 3 years. In the very short term (say, up to 6 months) people can control their weight via diet/exercise changes, but in the long term they generally can't. If we figured out what was going on and it turned out to be any of those other sorts of factors it would almost certainly be MUCH EASIER to control weight using those other factors than via diet and exercise.
That may be, and on an individual level it makes sense to focus on diet and exercise.
From a science and a policy point of view it makes a lot of sense to investigate what might be causing N% of the population to balloon in weight if they maintain their default diets and levels of activity.
//edited to add
Reason being that it might be possible to give someone a pill or a treatment that allows them to consume tons of calories and be sedentary without the health drawbacks related to obesity. From a policy point of view that would be a big win.
The default diet has increased and default levels of activity have fallen.
Put another way: the environment has changed. People have not.
For any given gradient across the population of desire to eat tasty food and desire to not engage in physical activity, the environment is progressively affecting more and more of the population.
I'm not sure you're responding to my post. I agree with regards to activity levels and caloric intake—but I'm saying it is worth investigating further.
It reminds me a lot of the lead hypothesis in regards to crime. The simple model would state that more people in prison and harsher law enforcement causes crime to decrease. However, if the lead hypothesis is true, then we can stop wasting resources on crowded prisons and draconian law enforcement, instead focusing on getting lead out of the environment. Or, more realistically, do something in between those extremes and at a policy level be far more successful.
> I agree with regards to activity levels and caloric intake—but I'm saying it is worth investigating further.
Absolutely. Science is worthy for its own sake, it doesn't need an extrinsic policy motivation.
As for falling crime, my understanding is that the criminologists are still arguing about that one. Especially since it seems to be a global phenomenon.
Check out the Mother Jones article by Kevin Drum. It's got quite a lot of references. The lead hypothesis is fascinating. The change in crime tracks lead levels internationally as well. While it is probably not the _only_ cause of the late 20th century crime wave, it's likely one of them, and might be a major one.
I have to wonder if there's a strong link to poverty or economic stagnation as well. With income disparity reportedly increasing by leaps and bounds, it's possible the crime of the last century and the recent violent uprisings in the US were all influenced by the economy.
It's intuitive, but I'm not sure if there's a causal link. The 20th century saw an incredible increase in income equality and that was the highest point in the recent crime wave. In fact, the increase in income inequality in the US over the last thirty years has coincided with the drastic decrease in violent crime, which is super interesting because it implies that those variables might be more independent than originally thought.
Really don't have to go back a century. A mere 30 or 40 years ago will do.
The obesity boom began around the mid 1970s with high fructose corn syrup, desk jobs (as deadly as smoking perhaps), the saturation of fast food (convenient, cheap low quality food), and the pasta + pizza (carbs carbs carbs) takeover.
Supposedly ~60 years ago the average American would have walked five plus miles per day. That may be down to a mile or less today from what I've read.
Comparing high school year book photos from the 1980s or early 1990s, versus my nephews & nieces and what their classmates look like today, the change is dramatic in a mere 20 to 30 years.
It seems to me that it's not just the extra calories, it's where they come from (sugar and refined flour carbs).
A couple of years ago I stopped eating sugar and bread. I went on a vaguely paleo diet, eating mostly meats, veggies, eggs, some dairy, and nuts, i.e. everything I used to eat minus sugar and bread. I did did not go hard-core paleo by any means. I lost 50 lbs pretty easily though I was not that I could tell eating less or less often. I ate when I was hungry, and stopped when I was full (easier to do, by the way, if you're not eating bread, pasta, or sweet things).
I never counted calories, so maybe I did consume fewer.
Recently I started eating some bread again. I really am a fan of pizza so I thought I would try indulging that every once in a while again. I have the occasional sandwich. Since doing that I gained 10 lbs back. Again I don't feel like I am overall eating more, but in my personal experience those types of carb-heavy foods cause weight gain much more than anything else.
My personal experience jibes with this. For many years I struggled to stay around 200lbs on a low fat diet. A year ago I tried the whole 30 and since then have easily stayed on a no grains or sugar diet and my weight is rock steady at 175 with no effort. I have always exercised a lot (15-25 miles a week running plus other activities) so no changes there and my blood work (cholesterol etc.) are good on both diets. Wish I had discovered this 20 years ago but happy I figured it out.
> The rise in net calories consumed per capita is pretty much entirely explains the observed variation.
True but I would be more specific than that. Basically we have two major trends going on:
1. Calories in per capita are falling slower than calories out per capita. For traditional, hand-tool-based farming, it required a lot of calories. Even animal-powered farming required a lot more than is required today. It's a bloody lot of hard manual work as my British friends would say. When one talks about net calories, one has to recognize that a hundred years ago people had to eat a lot more than today.
2. More reliance on high tech foods (HCFS, hydrogenated oils, etc, but also see frozen dinners, often which are loaded by excess corn sugar and oil). These are far from ideal dietary-wise.
These combine to mean fewer micronutrients, and an excess of macronutrients. But the lack of hard physical labor as the normal way of life is a major part of things.
So, I'm obese. I have no problems admitting that -- at my heaviest, I was 400 pounds, and while I'm nowhere close to the weight that I want to be, I watch my diet, work out every day, and try to live a life that promotes a great body image.
My mom is/was obese -- before she had a lap band installed. My dad is obese. My significant other is/was obese.
Being a 'bigger' person is something that I grew up in, and something that I attribute to being normal.
I didn't realize that being a "bigger" person was a problem until I went off to college and noticed that I was the exception, and not the norm. I only dated bigger women, because that's basically the only type of woman who would date someone who's bigger, and you can begin to see a cycle move forward again.
My SO got a full gastric bypass surgery in 2009 (after we had been through the second round of our post-grad work), and went from 400 pounds down to 150 pounds (for a 6' tall woman). She's been egging me on to get a lap band or bypass, but, I've already dropped a good 100 pounds from my heaviest weight, and will be able to drop the last 100 pounds on my own. My SO no longer has diabetes, heart issues, or anything like that -- other than some vitamin deficiencies, she's a pretty healthy (and stubborn) woman.
I don't think it's a genetic thing -- I think it's an environmental thing; you don't see a lot of chubby kids in a smaller household, and vice versa -- I don't see a lot of skinny/smaller children in a household that has obese or overweight people in it.
"you don't see a lot of chubby kids in a smaller household, and vice versa -- I don't see a lot of skinny/smaller children in a household that has obese or overweight people in it."
That's liable to be the case whether it's environmental or genetic (or, most likely, some sort of combination - though one may well dominate).
Isn't there a social problem in calling something genetic in that regardless of what genetic component may be a factor, it absolves one of personal responsibility. It reminds me of the "chocolate and wine are good for you" news stories. Very pleasing news, but ultimately net harmful.
Personal responsibility is only as good as a person's ability to choose. Since there is no dualistic free will, this ability to choose is based entirely within their brains and bodies, which are 100% the product of their genetics and environmental influences.
Thus, "personal responsibility" is a red herring if you are trying to get people to stop making bad choices. Instead, find out what neural, genetic, or environmental influence makes those bad choices more appealing than good choices, and fix that influence.
If this is the same study as a recent Ars article, then no choice is involved at all. Nobody chooses to have more or fewer immune cells converting white fat to beige fat.
Interesting article. One of the obvious problems in the typical discussion is that folks think of human bodies as mechanistic and identically so. I.e. we can reduce obesity to calories in/out because all human bodies are effectively identical or can be assumed to be such.
But we know that assumption is false (this happens with remarkable regularity in the sciences, that important theories that generally work are built on assumptions known to be false). People metabolize pharmaceuticals differently (google "cytochrome P450 defect", and try to convince me that such natural variation in metabolism of certain pharmaceuticals is a defect from any perspective other than big pharma's).
Now, the assumption, even though it is false, is generally useful because we know also that exercise changes metabolism. In other words, the human body isn't even static and so the abstractions generally work to an extent even though we know they are wrong. I think this sort of thing is why Heisenberg argued at book length that data does not imply theory.
But you are still assuming that the metabolism is effectively qualitatively identical. I.e, that the only thing changing is the quantity of calories burned rather than how the excess calories are used. Part of what makes this research fascinating is that it raises doubt about that, which isn't really surprising given what we know about Cytochrome P450 variance and pharmaceutical metabolism. Some people, for example, do not find vicodin effective because the pro-drug is metabolized much slower than the active metabolites....
Could you explain what's wrong with (calories in) < (calories out) == (weight loss)? This article doesn't refute this idea and specifically talks about it. This is just showing that some genetic mutations affect metabolism in ways that reduce (calories out) independent of activity level. This shouldn't be shocking. Metabolism varies across different people and across the same person over time.
Your body contains a feedback mechanism that is extraordinarily good at fine-tuning how much you WANT to eat and WANT to move in order to maintain its desired weight. You can fool this system in the short term, but most people can't fool it in the long run - it will correct - and likely overcorrect - any imbalance you try to impose. So the problem with the equation is that it strongly suggests that (calories in) and (calories out) are variables that are independent of one another and freely changeable by you, which they are not.
But if you still question this, let's consider an EVEN SIMPLER equation that governs your weight: we'll ignore calories and instead focus on MASS! Here's the equation:
(mass in) < (mass out) == (mass loss)
So if you want to lose mass, all you have to do is breathe out more than you breathe in and poop/pee more than you eat/drink. This is clearly literally true - if you lose mass you must have done that! (Okay, I'm simplifying a little - there's also dandruff, perspiration, hair and nail trimming and absorbing water through the skin - but those factors are probably small enough to safely ignore.) So go out and use my simple equation to lose mass!
But wait, you say that you can't MAKE your body exhale more mass than it inhales or excrete more mass than you consume on a consistent basis? Well, maybe you're just not trying hard enough. Exercise more willpower! :-)
I wasn't really commenting on this article, so much as on the comment I was replying to. But, what's wrong is that it's an oversimplification of how the human body regulates fat levels.
This oversimplification leads many to employ strategies of weight loss that revolve around simply measuring the calories they expend vs the calories they consume while ignoring the source of calories or other habits which affect hormone levels.
I'm not an expert on nutrition, fitness, biology, genetics or medicine... so you are free to dismiss my assertions if you require such a qualification.
Though, I do recommend reading some Nassim Nicolas Taleb, as he makes a much better case for what I'm discussing while also dismissing the idea that one needs to be an expert to recognize bullshit.
Also, I personally think articles drawing conclusions from scientific studies shouldn't be published before the study is replicated...
but of course, that would reduce the supply of articles for the ravenous pseudo-scientific commenter and we'd have to have more rigorous arguments on a smaller set of more rigorous information and people would run the risk of coming to all sorts of agreements and reducing click-through.
There are all kinds of cases where calories in < calories out which could result in weight gain. For example, if you already have an excess of body fat and you are building muscle quickly, remember muscle has 4kcal/g while fat has 9. If you are building muscle 1-2x breaking down fat, you will gain weight while losing fat, and expending more calories than what you are taking in.
Again, it's an abstraction which mostly works but it is also clearly not entirely true.
Obviously there are issues that can mask the weight loss from losing fat in the short term (water retention is a prime culprit here). However, in the long term (at least 8-12 weeks) the trend should be fairly obvious. The situation you described where someone is packing on 1-2 lbs of muscle for every lb of fat lost is very hard to achieve and generally only seen in beginners. Once the beginner gains are out of the way they'll see the same pattern as everyone else.
I am saying delta weight does not necessarily relate to delta fat. Delta fat contributes to delta weight but to say that other factors mask weight gain or loss makes me wonder if there is a fundamental confusion here...
I didn't say other factors mask weight loss. I said other factors mask weight loss from fat. Most of the time when someone says they want to lose weight they really mean they want to lose fat.
Taleb is a smart man, but considering he thinks carbs are "bad" for you, it's a classical case of someone who thinks being a master in one domain makes him a master in another completely-unrelated domain.
You're conflating calories-in/calories-out according to food labels and tabulated exercise studies with actual calories-in/calories-out, which is the simple physics which all the complex biological mechanisms eventually boil down to.
The food labels are averages, adjusted based on other averages. The exercise tables are averages, based on small studies. Any figure you come up with is an estimate, and unsurprisingly, they won't always work for outliers.
But for any given individual, on any given day, there is a net caloric balance. It will be different someone else's, given the same conditions. But there is still a net caloric balance.
"Individuals have varying responses to the environment" is not the same as "aha! physics is wrong".
No, I haven't read Taubes, I just have (and have had) friends across the entire spectrum of weight, height, fitness, etc. Some people can eat anything they want (including massive amounts of soda) and maintain a visible six pack with minimal exercise. Others in the same age range may have similar or better diets and struggle just to stay below 250lbs. That alone suggests there's more to obesity than caloric willpower.
Typically, when controlled studies are done on this, "naturally skinny" people systematically over-estimate their dietary calories and "naturally fat" people systematically under-estimate.
Under controlled conditions there is variation, but it is actually pretty modest. And it can be swamped by a habit of buying one Starbucks sugarcreamacino per day.
So the question isn't how do we get people to eat less food and exercise more, it's how do we get them to want less food and want to exercise? How can we turn the overestimators into underestimators?
This is where I think the change in environment is important. Food is cheaper, more easily available and calorically denser. Physical activity is down. Sleep quality and quantity have diminished.
Psychologists have done a lot of work on motivations, but mostly focusing on pathological cases which -- by their nature -- are the most difficult and irregular.
Obesity is a hot topic because it is epidemic. There may be a genetic predisposition in some people, but there is no way the gene pool could have changed so fast since Reagan got elected.
Most likely obesity has become the new normal thanks to some environmental toxin. (Ex. Bisphenol A). So there is someone to blame somewhere.
As for the in != out stuff I'll say that scientists have been wrong on this so long in face of the evidence; for instance, based on that theory long term weight control could be attained by cutting one cookie a day from your diet, which doesn't work. Also if you look at the metabolic charts, there are enough alternate pathways that the efficiency of metabolism could vary by 10% or more.
This is the point not made in the article. We did not historically have so many obese people until very recently in history. Looking at the 'fat' brothers in an old Guinness Book I noticed how much they resembled an average 'fat' person today. They aren't even near the far end of the overweight spectrum. Heck, even watching movies from the early 80s, what is often called 'fat' is considered average or normal today. We've changed our cultural definition of fat to make the average feel better about themselves.
And yet, when you watch a show from the 70s, say "Soap" (highly recommended - passes the test of time with flying colors), you'll notice that all the actors there -- and they all look considerably thinner than modern actors (e.g., take Friends for a nineties comparison). Standards have changed, regardless of Hollywood, and you can measure relative changes (though not absolute values) on through Hollywood.
If you expend more energy than you take in via calories, you lose weight, period. With a rational approach to food intake, that 10-15% the researchers claim is like cutting the crust off of a sandwich. It's nothing. You don't see a lot of obese animals in nature, regardless of any genetic metabolic mutation, because they have to actually work to acquire their food.
It's funny that when I see people stick to traditional diets, they gain weight at a vastly slower rate than people who eat fast food and drink sodas. They may still end up being technically obese, but it will be at age 70 instead of age 35.
Disclaimer: I am not a doctor, just someone who is curious about how the body works on a high level.
To better understand cause and effect, a question that Peter Attia asks is that, do children eat more and grow (gaining weight as they age), or is it because they are growing that they eat more? Nutrition turns out to be a lot more complex than just calories in and calories out. It looks like that is a manifestation of something deeper, like growth hormones triggering a different type of metabolism.
He asks the same question about obesity. Do people get fat (elevated number of triglycerides stored in the fat cells) because they are eating more than expending energy? Or, are they eating more because of hormonal imbalances? He (along with many other doctors) suggest that it is actually the effect of insulin that causes the body to be conservative with the expending of energy. Insulin resistance also leads to diabetes, which is strongly correlated with obesity. So the hypothesis is that it is out of control insulin (due to sugar intake, HFCS, simple carbs, prevelant in american diet) that is the cause for the obesity epidemic, and not just less exercise (although exercise can be used to eliminate the excess glucose in the body which triggers the insulin response).
Calories in and calories out are not simple knobs that anybody can tweak at will; they are complex functions that, if we could define them, would depend on genetics, temperature, types of food eaten, energy expended recently, etc. It's meaningless to say "CalIn==CalOut" when each is defined in terms of the other.
That's proof there exist complex systems that can be usefully modelled simply. In no way does it demonstrate that all complex systems can be usefully modelled simply or give us any confidence that the human body is such a system.
My car can't even observe speed exactly, it's off by a few km/h. It doesn't matter because the cops measuring speed expect the error and subtract the margin for me.
For "eating less to lose weight" you're looking at megajoules/week change. Theres plenty of room for impreciseness here.
There's been a misunderstanding. I agree with you that direct caloric balance is unobservable on an individual basis, it can only be approximately estimated.
I'm saying that weight and appearance are observable, and that diet is adjustable.
Want to gain weight? Change your diet a bit, observe the results over the following weeks. Repeat until satisfied.
Want to lose weight? Change your diet a bit, observe the results over the follow weeks. Repeat until satisfied.
Some people do these with old-fashioned calorie counting. Some with specialised diets. Some but dropping sweet drinks.
But unless you first internalise the locus of control, you won't get anywhere.
But if tou have one engine going downhill and another engine going uphill they are going to be burning different amounts of energy.
We know that some gut flora encourages obesity; we know other flora encourage thinness; so having a method to make sure obese people don't have the fat-encoiraging flora and do have the thin-encouraging flora at least gives people a fighting chance.
> But if tou have one engine going downhill and another engine going uphill they are going to be burning different amounts of energy.
Yes. The goal is to maintain a particular speed.
> so having a method to make sure obese people don't have the fat-encoiraging flora and do have the thin-encouraging flora at least gives people a fighting chance.
Sure, I think that's a very promising line of research that may make it easier for many people to modify their appetites. But for any given gut flora, the basic logic still holds. Just as for any given steam engine, the Watt governor works on the same principle.
>If you expend more energy than you take in via calories, you lose weight, period. With a rational approach to food intake, that 10-15% the researchers claim is like cutting the crust off of a sandwich. It's nothing. You don't see a lot of obese animals in nature, regardless of any genetic metabolic mutation, because they have to actually work to acquire their food.
In theory yes, but the vast majority of people who try to lose weight through diet fail. And obese people who are forced to stick to a diet have the metabolisms of starving healthy people - their body desperately trying to return to it's previous weight.
The diet works. Their habits are a different matter. There is no such thing as "body desperately wanting to return to an old weight." Most people who screw up on their diets end up weighing MORE than before. That's because their approach to food is screwed up, not their genetic disposition to store fat.
It has nothing to do with habits. Diets almost always fail, and those on them almost always return to their previous weights. Far more than can be explained by "habits".
Obese people who go on diets have the metabolisms of starving people. While on a diet they burn 24% fewer calories per square meter than a normal person.
In experiments normal people forced to eat huge amounts of calories gain weight. But as soon as the experiment stops they quickly return to the previous weight. During the experiment their metabolisms increase by 50 percent, and they need far more calories to maintain the weight.
"The body’s metabolism speeds up or slows down to keep weight within a narrow range. Gain weight and the metabolism can as much as double; lose weight and it can slow to half its original speed."
Also it's really easy to test if something is genetic. Just look at identical twins. Twins have the same weights even when raised in entirely different environments. "Weight is more strongly inherited than nearly any other condition, including mental illness, breast cancer or heart disease."
If you expend more energy than you take in via calories, you lose weight, period.
I think your phrasing is important here, because there is a lot of debate about "Calories in, calories out" especially considering studies showing that not all calories have equal effects on the body. Generally though the first law holds, the distinctions are about what timeline...
Based on the paper, it appears that they performed targeted mutations to manipulate the Mrap2 gene and fed the mice equal quantities of chow, and then they did the tests described in the parent article. At least to me, this is strong evidence that this gene affects obesity in mice.
DNA may or may not be one factor; gut flora may be another.
The fact is that we now have proof that 2 mice can eat the same energy, burn the same energy and poop the same energy, and yet 1 will become fat and the other won't.
Say what you will about responsibility when it comes to obesity, you can no longer argue with authority that "calories in - exercised calories out = weight" due to this single counterevidence.
I have often wondered if my shit would burn well compared to people who put on weight. I can increase the amount I eat while really doing nothing and I still remain skinny. I put on muscle if I exercise and eat, but I do seem to have a digestion that ignores stuff unless I am busy. Though it might just be that when I am not busy I tend to poison it with spirits.
what a terrible headline. a subset of mice have a predisposition towards obesity, so america's exploding obesity epidemic may not be the individuals fault despite:
#1 genetic ratios couldn't possibly be changing that much
#2 most people who do go on diets and exercise DO lose weight.
#3 as the article points out, the gene in study is rare in humans.
Your #2 point is false. Most diet/exercise programs appear to "work" in the short run, but fail in the long term. Very few people who diet haven't gained the weight back and then some within 3 years. The sad truth is that we don't yet have any GOOD advice to give overweight people who want to not be overweight. Telling them to diet to lose weight is, in practice, terrible advice.
The headline is fine if you keep in mind that the subject of the study is only one of a number of mechanisms by which people could be not at fault for their weight gain. There's things like the "fat virus" (http://en.wikipedia.org/wiki/Infectobesity). There are epigenetic factors - we're just learning that how well your grandparents ate can affect your health. There might well be chemical or medical factors too - overuse of antibiotics changing the bacterial load is a common suggestion.
We know that dieting is a terrible method for losing weight. It's untrue to say thT most people who diet lose weight - they only do so in the short term while they maintain that diet. As soon as they stop they regain weight, often settling at a higher weight.
Unless by "dieting" you mean "permanent lifestyle change" which is fair enough.
I am addressing the article's statements about mice not loosing weight despite changing their diet and exercising. the length of time they loose the weight is less important, and the fact that the reason why they put the weight back on after reverting to their previous habits only works against the article that argues the obese may be at the mercy of their genes - diet and exercise wont help them.
We can play the blame game but we can't disregard the laws of thermodynamics.
Too much energy intake and not enough expenditure means that energy goes somewhere. We can examine the science and sociology of how it happens, but the only thing pieces like this accomplish is to make people feel better about their health issues and filled the coffers of snake oil salesmen.
Don't read the article and read the studies instead.
Given the less controllable tail end of the process creates a widely variable amount of flammable solids and gases, it isn't as though it is just the inputs you should be considering. I'm skinny and fairly sedentary and I know damn well that with a different set of genetics and the same behavior, then I would be fat. Also, seems that in terms of lifespan, I may be better off being a bit overweight than slightly under, really, the benefit seems mainly aesthetic for most people, which is a crap reason to guilt-trip a society.
For the unfortunate minority that truly does have a very strong genetic component, the fact remains that eating slightly less - just 10-15% less, will allow them to match their metabolism.
This is not to say we should "blame" people - social and environmental factors are very important. Lack of sleep due to too much work / artificially lit environment causes more eating, lots of food is engineered to be super tasty for us, there were no cookie trees in our ancient past :)