Can dieting affect your mood?

For most people, the answer to this question may seem obvious. Sure, sticking to a weight loss program can make anyone cranky. Beyond purely psychological reactions, however, new evidence begins to suggest that the type of carbohydrates you choose as part of your diet plan may actually cause a physical reaction that results in a bad mood.

Putting comfort food to the test.

A group of researchers at the Friedman School of Nutrition at Tufts University conducted a study in which healthy, overweight adults were provided with two types of carbohydrates: one group ate foods with a low GI, and the other group ate foods with a high GI. “GI” refers to “glycemic index,” which measures the ability of a carbohydrate to raise blood glucose, a precursor to diseases such as diabetes. Highly processed foods made with refined flour and sugar often have a higher GI, whereas whole foods tend to have a lower GI.

Many previous studies had found that high GI diets had a negative effect on mood, which supports the “carbohydrate-depression hypothesis,” suggesting that high carb diets improve mood through increased delivery of tryptophan to the brain. For most of us, that might translate to the “comfort-food thesis”—we turn to high GI foods such as mac ‘n’ cheese, cookies, or mashed potatoes to feel better when we’re stressed or blue.

A “sugar high” could end up being a “sugar-low.”

What the Tufts group discovered, however, was exactly the opposite: higher GI foods caused negative changes in mood, whereas lower GI foods had no effect on mood. What makes their research compelling is that the study was exceptionally controlled, which increases the likelihood of a direct cause and effect relationship between GI and mood while dieting.

So next time you decide to break your diet and reward yourself with a special treat to lift your spirits, you might want to grab the apple instead of the ice cream cone.