A couple of times in the last few months, I’ve seen this very odd statistic that the average American consumes 3790 calories per day. This is usually used in conjunction with some argument about why Americans are overall so obese. For instance, here is one such thing from diet-blog.com.
Do Americans Eat 3,790 Calories Per Day?
I had thought that this number can’t possibly be correct: if it were, we wouldn’t have a 35% obesity rate, we’d effectively all be dead from exploding. As an adult male my age, you might anticipate that my caloric needs would amount to (say) 2400 calories a day (I’m a tall guy). That means that if I consumed this ‘average’, that I would have a caloric surplus of 1390 calories every day. There are about 3500 calories in a pound of fat. That means I’d gain a pound every two and a half days. 144 pounds every year! That can’t possibly be correct.
Until recently, I didn’t research or spot the error, but now I can tell you what it is.
The “consumption” referred to here isn’t the amount eaten. It’s merely the amount food which is available to consumers. From the USDA’s FAQ on the source of these numbers:
Q: Does the Food Availability (Per Capita) Data System measure actual consumption?
A: No. The data system, which consists of three data series, does not measure actual consumption or the quantities ingested. The data are not based on direct observations of consumption or on survey reports of consumption. They are calculated by adding total annual production, imports, and beginning stocks of a particular commodity and then subtracting exports, ending stocks, and nonfood uses. Per capita estimates are calculated using population estimates for that particular year. However, ERS’s food availability (per capita) data are useful for economic analysis because they serve as indirect measures of trends in food use. In other words, the Food Availability (Per Capita) Data System provides an indication of whether Americans, on average, are consuming more or less of various foods over time.
Roughly speaking, this 3790 calorie per day number is derived from the vast surplus of food which is produced and sent to consumers. It has nothing to do with the amount that is actually observed to be eaten.
Sadly, I see this number echoed time and time again on diet blogs, usually in the form of cautionary tales about ‘someone I know who probably does eat that much’. It’s nonsense.
As a person’s weight increases, so does their basal metabolic rate, as well as the amount of calories they are capable of burning. A person of 6’4 at 200 pounds has a bmr of about 2,000 calories, where the same person at 300 pounds might have a bmr of 2,600. Beyond that, a heavier person requires more muscle mass to pull their weight, resulting in an exponential amount of calories burned. The amount gained may be incrementally higher each year, but not so much that you would notice on a daily basis.
It’s quite difficult to calculate one’s caloric intake and output, much less a population. People typically underestimate calories by 20%, on average. The 3,500 is also just an average. A person’s extra fidgeting, shivering or sweating might affect the day’s burn rate.
There is some theory on a persons “natural body weight”. Watch the BBC documentary “Why are thin people not fat?”
http://www.youtube.com/watch?v=_6-A0iHSdcA&feature=related
I have no time for people who eat like pigs and then search for magic pills, diets and programs. If you eat too much, you’ll be fat no mater what. And i’m not particularly slim but I actually do run and feel healthy, without feeling hungry constantly. Get a grip people!