There is no doubt that consuming large amounts of sugar will pack on the pounds, which is something to be aware of with the growing epidemic of obesity in the US. However, no matter how bad sugar may be for us, high fructose corn syrup (HFCS) is worse. A recent study published in the Journal of the American Medical Association (JAMA) has found that the body and brain react to fructose differently than glucose, causing us to eat more and to store those sweet calories as fat. So better to raid the sugar bowl than the Aunt Jemima syrup for your morning oatmeal!
The Effect of Fructose on the Brain
The study was performed by researchers at the Yale University School of Medicine, who recruited 20 people of normal weight to test the effect that fructose has on the brain. Functional Magnetic Resonance Imaging (FMRI) was used to measure the response of the subjects’ hypothalamus as they consumed sweetened drinks. The hypothalamus is involved in the processing of reward and motivation, in addition to helping to regulate appetite.
Each volunteer was given a 300 ml cherry flavored drink that was sweetened either with 75 grams (about 300 calories) of fructose or the same amount of glucose. The drinks were provided at sessions one to eight months apart and were given in random order, so the subjects were not aware of which drink they were getting. The researchers also took samples of the volunteers’ blood and asked them to rate how hungry or full they felt.
The FMRIs showed that the hypothalamus registered significantly different activity within 15 minutes of ingestion based on whether the subject had taken the fructose drink or the glucose drink. Fructose caused a small spike to the activity in the hypothalamus, whereas the glucose led to reduced activity in this area. Only the glucose drink prompted feelings of fullness, so that people eating a meal with a fructose-based beverage were more likely to keep eating than those with the glucose drink.
How Fructose Is Metabolized
Although on a molecular level, fructose and glucose look similar, they are each metabolized differently by the body. The release of insulin from the pancreas when we eat a meal or drink a sweetened beverage is what helps to tell our body that it is full and reduces feelings of satisfaction from eating. Fructose spurs a lower release of insulin than glucose. Fructose also reduces the amount of circulating ghrelin less than glucose does. Ghrelin is a hormone that makes us feel hungry.
When fructose is consumed, it is metabolized directly by the liver, which immediately stores the compound as fat. We end up stuck in a vicious cycle, eating food and beverages that go directly to our waistlines and never feeling satisfied because we are not getting hunger satiety signals from either reduced ghrelin or a sufficient release of insulin. This makes us crave even more food in an attempt to feel full.
HFCS contains about 55 percent fructose and 45 percent glucose. Meanwhile, sucrose (simple table sugar) is evenly divided at 50 percent fructose and 50 percent glucose. It may not seem like a huge difference, but it can add up in the pounds that you accumulate over time.
Satisfy Your Hunger
Scientists from the Oregon Health & Sciences University in Portland, Jonathan Purnell, of the Division of Endocrinology, Diabetes, and Clinical Nutrition, and Damien Fair, of the Department of Behavioral Neuroscience, co-authored an article on the subject that appeared in the same issue of JAMA. They wrote, "A common counterargument is that it is the excess calories that are important, not the food. Simply put: just eat less." They continued, "The reality, however, is that hunger and fullness are major determinants of how much humans eat, just as thirst determines how much humans drink. These sensations cannot simply be willed away or ignored." They advised consumers to eat food that satisfies hunger if they want to control their weight, and avoid those foods and ingredients that do not. Therefore, if you decide to eat or drink something sweet, choose the glucose over the fructose.
Researchers are now undertaking a study of overweight people to see if their brains function any differently in relation to fructose and glucose. Your best bet is to avoid processed foods and sweetened beverages. Over time, you will likely see a reduction in your weight.