Why are we getting so fat? The conventional wisdom is that we are getting fat because we eat too much and exercise too little. There’s ample evidence to support this view, but lately an alternative explanation for the obesity epidemic has gained currency.
Gary Taubes, a prominent science writer, and Dr. Robert Lustig, a UCSF Professor of Pediatrics, among others have suggested that all calories aren’t equal. They attribute the rapid rise in the prevalence of obesity to the increased sugar and refined carbohydrates in our diets.
Taubes suggests that calories from fructose, a type of sugar, have a greater impact on weight than calories from other sources. Fructose effects insulin which determines fat accumulation. Fructose is metabolized primarily by liver cells. Some of the fructose is converted into fat which accumulates in the liver making it more resistant to the action of insulin. This leads to elevated levels of insulin and the accumulation of more fat in the fat cells. Thus obesity is the result of fattier fat cells after consuming foods containing fructose.
Dr. Lustig has an equally damning view of sugar. He suggests that, like alcohol, nicotine, and opiates, sugar affects the brain’s pleasure centers so many of us become sugar addicts. Like other types of addiction, it takes ever increasing amounts of the substance to obtain the desired effects. In other words, we need to continually eat more sugary foods to get the good feelings. As a result, we get fat. He suggests that the sale of sugar should be regulated like the sale of alcohol and tobacco.
As you would expect, not everyone agrees that sugar is toxic. Dr. David Katz of the Yale University School of Medicine agrees that there’s too much sugar in our diets but doesn’t think that sugar, by itself, is evil. He points out that mother’s milk is very sweet and fructose, the type of sugar Dr. Lustig thinks is most harmful, is found in fruit. No one is suggesting that the sale of berries and apples needs to be restricted.
Whether sugar has unique properties causing weight gain, or if it’s just adding unnecessary calories is likely to be debated for some time to come. What is not controversial is that we’re consuming too much of it. To cut back, the best place to start is with sugary drinks.
Unlike breast milk, apples, or even Twinkies, sodas, sports drinks, energy drinks contain large amounts of sugar but don’t provide any nutrients – it’s all empty calories. Although fruit juices have some nutritional value they also contain large amounts of sugar. Parents often view orange juice as an essential source of vitamin C for their kids but it’s unlikely that children with an adequate diet will be deprived if they skip the orange juice. Likewise, cutting back on apple juice and grape juice will avoid unnecessary sugar.
Dr. Lustig also recommends eating carbohydrates with fiber. He suggests that fiber will lessen the insulin spike that you would otherwise get with carbohydrates. So, if you’re going to buy a carbohydrate rich packaged food look at the list of ingredients and aim for three or more grams of fiber.
Is a calorie just a calorie or are some calories more dangerous than others? I don’t think we’ll have a definitive answer for a while but in the mean time we can still cut back our consumption of sugars.