Over the past two to three decades, people in western countries have been getting fatter, and the phenomenon is spreading to some industrializing countries, too, such as China and India. Doctors are particularly concerned about the skyrocketing numbers of overweight and even obese children.
University of Colorado nutrition researcher Dr. Jacob Friedman notes that birth weight is also on the rise. His research indicates that childhood obesity might actually start in the womb.
Extra weight puts people at higher long-term risk for a host of diseases, from arthritis to heart attack. One condition - known as fatty liver - used to be a problem seen in obese adults in their 40s and 50s. Now Friedman says doctors see it in children.
"That fatty liver disease can be benign, or it can progress to hepatitis-like symptoms, where there is fibrosis and actually the need for a liver transplant, so excess deposition of fat accompanied by obesity in your liver, in the longterm, if it's in a child, has very profound implications, and that's a very common concern with childhood obesity - that we are seeing liver fat where it shouldn't be."
Friedman and his colleagues studied 100 pregnant monkeys. They gave some a regular diet with about 15 percent fat and offered others a diet with about 35 percent fat. Much of that was saturated fat - the kind that, in general, comes from animal products.
"In fact, 35 percent fat is about what the typical American, average person eats," Friedman says. "So those diets were self-selected. They were not force-fed. They were not prevented from any exercise. They were glad to just eat this diet as their normal caloric intake. And they did eat more calories... most of them gained more weight on this [higher-fat] diet, but not all of them did."
Friedman and his team examined the fetuses of some of these monkeys and found that the livers of their babies were fatter, even before they were born. It didn't matter whether or not the mothers had gained weight on the high-fat diet. Their babies still had more fat deposited in their livers. Friedman says in many cases, the babies didn't weigh more when they were born.
"…but they were fatter. And as they progressed to about 18 months... their fat content just continued to go up and up, and they had all the signs and symptoms that they might be on their way to developing diabetes."
Friedman notes with dismay that these baby monkeys were only being breast fed by their mothers who were eating the high-fat diet, indicating that the fat was also being transmitted in breast milk.
In the United States, guidelines for how much weight pregnant women should gain are currently under review. Friedman says in addition, doctors may need to consider telling women the kind of diet that's best to eat during pregnancy and caution them about eating too much fat.
His research is published in the Journal of Clinical Investigation.