Rates of obesity and insulin resistance have climbed sharply over the past 30 years. And researchers have established that the parallel rise in fast food consumption and sugary drinks has had a direct effect on obesity in America. But is this message reaching consumers? Or is it that we are so ‘hooked’ on these foods that we can’t seem to kick the habit?
“The evidence that fast food and soft drinks are drivers of the pandemic of childhood overweight and obesity is very impressive,” said Philip James, President of the International Association for the Study of Obesity. James is also one of the authors of the World Health Organization (WHO) report on the prevention and management of obesity.
Despite the warnings, every day nearly one-third of U.S. children aged 4 to 19 eat fast food, which likely packs on about six extra pounds per child per year, a study of 6,212 youngsters found. The study also noted that fast-food consumption has increased fivefold among children since 1970.
Consumption of sugary drinks has also increased dramatically. U.S. consumption of carbonated soft drinks alone, which is now around 50 gallons per person (including children) per year, has risen ten-fold since the 1940s.
A new report from the Centers for Disease Control (CDC) says about half the U.S. population indulges in sugary drinks on a daily basis. Boys age 2 – 19 drink the most with 70% drinking sugary drinks every day. The amount of calories this adds to our diet is staggering: Teen boys average 273 calories a day from sugary drinks, teen girls add 171 calories, men age 20-39 add 252 calories and women 138 calories. Based on a 2,000 calorie diet, that’s as much as 13% of total calories or an additional 4-6 pounds per year.
How these foods make you fat
Some of the properties of fast food, including its high glycemic index and its fatty acid composition, induce hyperinsulinemia (too much insulin in the blood) and the development of insulin resistance. Insulin resistance manifests in weight gain, especially around the abdomen and can lead to high blood pressure and cholesterol levels, type 2 diabetes, and heart disease.
Researchers believe that hyperinsulinemia and insulin resistance may in part be responsible for leptin resistance. Leptin is a principal modulator of body weight and metabolism. Leptin resistance occurs when the body fails to transport leptin to the hypothalamus where it would normally signal the body that it is satiated or full. Without leptin, food cravings and weight gain occur because the body believes that it is hungry and goes into a state of continued fat storage and food consumption.
Furthermore, insulin resistance interferes with the “pleasure and reward” system in the brain which is controlled by dopamine and dopamine receptor sites. When dopamine signalling is impaired, we feel compelled to consume more food in order to achieve an acceptable level of satiation and reward. There is some research to support that this pattern may also lead to a form of “sugar addiction” in which increasing amounts of sugar are required to satisfy a “sweet tooth.”
Therefore, the consumption of fast food and sugary drinks affects neurochemical processes that set in motion a viscous cycle of increasing hunger without satiety or satisfaction.
Kicking the habit
Recent studies suggest that obesity is now a bigger threat to the country's health than tobacco. In the past 15 years, the smoking rate fell by more than 18 percent, but the rate of obesity jumped by 85 percent. While smoking is said to shorten your life by an average of 10 years, obesity could shorten your lifespan by as much as 13 years.
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American Heart Association
World Public Health Nutrition Association
American Journal of Clinical Nutrition