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Comment by dkural | Hacker News Reader

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 :)

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In all this discussion of HFCS and other things, this is the chart I'm shocked nobody ever mentions: http://thesocietypages.org/graphicsociology/2011/04/11/nutri....

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.

http://www.webmd.com/diet/news/20070820/obesity-virus-more-b...

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.

This "most people don't keep it off" soundbite is usually based on studies of pathological cases in obesity clinics.

Not the general population.

I'm in the general population. I peaked at 139kg 4 years ago. I've been around 100kg for about 18 months now.

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.

http://www.motherjones.com/environment/2013/01/lead-crime-li...

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.

HFCS is basically unique to the US food supply.

Everyone else is getting fat without it.

The rise in net calories consumed per capita is pretty much entirely explains the observed variation.

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.

Epigenetics?

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