Activity levels and obesity: a summary
Clearly, one important component of the obesity epidemic in the U.S. is our rather alarming state of inactivity. But, lack of exercise can not fully explain things. For example, we all know some people who get virtually no exercise and are not overweight. Some people do try hard to get regular exercise and still gain weight year after year. It can’t be just inactivity. I do not mean to imply that lack of at least reasonable physical activity (I won’t try to define what I mean by “reasonable”) is not an important factor in explaining the obesity epidemic. Even 100-200 “extra” calories burned per day through physical activities, can have a profound effect on energy balance; all other things equal, each 100 calories per day in increased energy expenditure translates into about 12 pounds of fat not gained per year!
What about the caloric intake side of the energy balance equation?
If a person has an appropriate body weight at time-point A and then increases calorie intake by 100 calories per day (assume no change in energy expenditure),there would be about a 12 pound increase in body weight at at point B one year later- I bet you figured it out before I told you the answer! So can we put part of the “blame” for the obesity epidemic on increases in calorie intake? The answer is “you bet.” Studies have shown that on average, people in the U.S. are eating about 200 calories more per day than in 1977- that’s a 10% increase in calories consumed per day. How can this be? Well, I can’t give you an easy answer but I can give you some possibilities.
Food is cheap
Food in the U.S. is really cheap. I know that some families still struggle to afford enough high quality foods to allow good nutrition and adequate calories. But for most people in the U.S. it’s almost a free-for-all; at present, we spend only about 17% of our incomes on food, including eating out. That’s far less than what we spent on food 30 years ago as percent of income. We already know that many of us have brain appetitie centers that are not satisfied with just enough calories in to maintain body weight (or to gain weight appropriately for a child). So easy access to really cheap food helps to explain where the 200 “extra” calories per day come from.
Portion sizes and types of foods
Partly because food is so cheap, we as a nation have made drastic changes in portion sizes. We do it at home and restaurants have done it to us when we eat out. I remember when a “regular” hamburger was the only size available at McDonalds (it only cost 15 cents then). Now at McDonalds or any other fast food chain resturant that sells hamburgers, we can feast on a a megasandwich, which is incredibly cheap considering the gigantic number of calories (mostly fat calories, of course). At home and in resturants we use much bigger plates than in the past- about 30% bigger over the past 30 years so I am told. The psychology of plate size is fascinating. Left to our own devices, we will take about 30% more food if our plates are 30% bigger. It’s the same for glasses; people using a short fat glass will take about 30% more liquid to drink than if the glass is tall and slender.
Who is to blame for portion-size inflation and for such cheap food?
I don’t know that anyone in particular is to blame for the mess we have created. The “why” of our cheap food is complicated and I refer you to the books I mentioned in an earlier posting (“The Omnivore’s Dilemma,” by Michael Pollen, and “Fast Food Nation,” by Eric Schlosser). In a nut-shell, our government subsidizes the production of much of the food we eat, particulary soy bean and corn-based products (in about 70% of what we eat!). That’s why it’s so cheap. Don’t get me wrong, I am not advocating more expensive food just to keep us from eating as much and as much that is not very good for us. It’s all so complicated. We are weak (at least our appetite centers are) and the food advertisers are strong. The food industry has a big problem. They have become so efficient at food production that we have gigantic surpluses; the food industry produces about 500 calories more per day per person in the U.S. than we can stuff into our mouths. Of course, no one is forcing us to eat so much and so much that is of questionable nutritional value.
What about the children?
The one real problem I have with the food industry is the way it puts so much energy into getting children to eat more and more of what is of questionable nutritional value. Children are bombarded with food advertising on television, billboards, and even at the schools. The entertainment industry plays a part in all of this too by working with the fast food industry to entice children to go eat fast food because they can get some little toy creature. Even so, parents could control this if they would. And of course they should take control; remember, most overweight children become overweight adults.
- Obesity: Activity Levels
- Obesity: Psychological Factors