A team of academic cardiologists published a paper in the April 15, 2014 issue of the Journal of the American College of Cardiology, one of the world's most prestigious cardiology journals, entitled "Obesity and Cardiovascular Disease."
One of their conclusions is that: "Progressive declines in physical activity over five decades have occurred and have progressively caused the obesity epidemic." They support this conclusion with data showing that energy expenditure at work and doing household chores has decreased significantly over the last 50 years.
We burn fewer calories on the job and in household chores, and this decrease in caloric expenditure has not been matched by a decrease in caloric intake.
Humans, like every other animal on earth, adjust our energy intake to match our energy expenditure. In his wonderful myth-smashing book Good Calories, Bad Calories, Gary Taubes points out that tailors on average consume 2,500 calories and lumberjacks 4,500.
How could it be otherwise? Imagine an animal in which energy intake and energy expenditure are truly independent of one another. Maintaining a normal weight then becomes a matter of chance. But living organisms must be efficient to survive, and energy balance is at the very heart of this efficient functioning.
That's why it seldom works to tell someone who wants to lose weight to just increase energy expenditure. Just run around the block every morning before work and keep everything else the same and you'll lose weight. It's impossible to keep everything the same. The energy expenditure causes energy depletion, and our brains through a complex cascade of hormones cause us to be hungry and to eat. Even if one can resist the hunger, and most of the time this semi-starvation state cannot be resisted indefinitely, our bodies have other ways of matching energy supply and energy demand.
Use up all of your available energy on that run around the block and your body will find other ways to lower energy consumption, like turning down the little furnaces in your cells a bit or decreasing mental activity. You might not even feel the slight drop in temperature or the slowed brain functioning.
If these academic cardiologists are right and the energy we burn from work and household chores has dropped and we haven't increased our energy demands in other areas, a well-functioning organism should decrease its caloric intake automatically. That's how we do it with thirst and that's how we are supposed to do it with hunger.
But that is not what's happening. According to the USDA, the average daily caloric intake increased by 530 calories between 1970 and 2000. Why aren't we successfully matching energy demand with energy supply? Something has gone wrong. If we burn less, we should automatically consume fewer calories. Why don't we?
At least part of the answer can be found by looking at the role that sugars play in our diet. We consume vast numbers of calories from sugary drinks and the other added sugars in our diet. Sugar-sweetened beverages are the single largest source of added sugar and the top source of energy intake in the U.S. diet. These calories do not produce fullness and therefore escape the body's physiologic efforts to remain in energy balance.
There has been a paradigm shift, a scientific revolution, in our understanding of sugar's toxicity and it's relationship to obesity and cardiovascular disease. As in all paradigm shifts, it takes time for the new knowledge to be disseminated and accepted. Perhaps that is the reason that the present journal article discusses obesity without mentioning sugar.
If, as the article claims, the cause of obesity is a decrease in energy expenditure, one obvious remedy would to increase our energy output. How much would we need to increase our energy expenditure to be in balance?
U.S. children and youth obtain on average 224 calories per day from sugary drinks, about the amount of sugar in one 20-ounce soda. A 50-pound child would need to walk for more than three hours at three miles per hour to burn off all of those calories. A 200-pound adult would need to walk for more than 45 minutes.
Given that a significant number of people consume two or more sodas a day, and foods that contain added sugar, preventing and reversing obesity will require drastically reducing our sugar intake.
Let's not confuse the public now by blaming obesity on lack of physical activity. We do need physical exercise. No argument. But it's the sugar in most cases that is the cause of obesity, and which has now also been linked directly to heart attacks, strokes, diabetes, high blood pressure and cancer.