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Many adults know they need to lose weight, either a little or a lot. Most adults also have carbohydrate cravings, often to eat a lot or a lot more. If there were just some way to squelch the carb cravings most of us have, weight loss would be a lot easier, but until recently that's been a lot easier said than done.
With Carbohydrates, The More You Eat, The More You Want
For many years, doctors and researchers studying weight loss did not really understand what it is that drives our appetites for sugars, sweets, and carbohydrates in general. Some researchers thought the primary causes for carbohydrate addiction might be genetic, that some people are just born to crave sweets. Others supposed carb addiction was primarily a matter of social conditioning, The real reason most of us crave carbohydrates, however, turned out to be a paradoxical process that nobody really expected.
It turns out that when carbohydrate addicts eat small amounts of "pure sugar," high-glycemic index food, our bloodstream glucose levels go down instead of up, compared to "healthier," lower-glycemic index food.
Investigators from Boston Children's Hospital in Massachusetts recruited 12 overweight or obese men aged 18 to 35 to participate in a study of the role of sugar in stimulating carbohydrate cravings. Unlike earlier studies that had looked at differences in the way the body responds to, for example, chocolate candy bars and broccoli, this study looked at differences in the way the bodies of overweight people respond to foods that look the same and taste the same and have the same number of calories, but have different amounts of sugar.
On one test day, the volunteers were given a 500-calorie shake that had a high glycemic index (87), that is, it contained a lot of sugar that went into the bloodstream quickly. On another test day, the volunteers were given a 500-calorie shake that looked and tasted the same, but had very little sugar and a lot of fiber, giving it a low glycemic index (31). With the second shake, any digested sugars entering the bloodstream more slowly. One both occasions the volunteers had brain scans and blood tests to measure the effects of their meal (or snack, from the perspective of an overweight person).
The surprising effect of consuming more sugar was that blood sugar levels went down instead of up. In these non-diabetic men, the difference in blood glucose readings was about 0.6 mmol/L (9-10 mg/dl), which is just enough to stimulate hunger. The volunteers consistently reported that drinking the high-glycemic index shake made them hungry for more, while drinking the low-glycemic index shake left them feeling full.
This Is Your Brain On Sugar
The volunteers' brain scans were also different after consuming the two different shakes. Drinking a sugary, high-glycemic index shake activated a part of the brain called the nucleus accumbens, which is activated in addiction. The unexpected brain activation occurred in all 12 men participating in the study. From this the researchers concluded that easily digested carbohydrates, such as sugar, white bread, and instant mashed potatoes, activate pleasure centers in our brains that make us want to eat even more.