You Are What You Eatby Shefali Sabharanjak, PhD | April 26, 2013
Excess food intake makes you fat. High calorie foods make you gain excess fat. Excess carbohydrates and saturated fatty acids get taken up by fat cells and get converted into fatty acids stored within them. This is what we know of the straightforward relationship between diet and obesity. Yet, the relationship between food choices and obesity is not so linear or short-term. Food choices and obesity have a more complex interdependence.
In a recent study, Hispanic women volunteers were subjected to functional Magnetic Resonance Imaging (fMRI) while they were shown images of food as well as non-food items. These participants were also asked to state their emotional responses to food in terms of desire to eat the food items they were shown. Responses from the fMRI images were graded as per the contrast between activation patterns seen with high calorie foods versus those for non-food items. This study, to be published in print later this year, demonstrates that images of high-calorie foods elicited a greater response in the striatum nigra region of the brain, indicating a reward response. Images of high calorie foods also increased appetite and the desire to eat sweet as well as savory foods. It follows that repeated intake of sugary foods can only increase obesity.
Interestingly, the striatal response varied proportionately with the waist circumference of the participants. The overall BMI of the volunteers had no correlation with the activation response demonstrated to calorie-rich foods.
The outcomes of this study are hampered by two facts: First, the number of volunteers is small – just thirteen. Second, the volunteers were exclusively Hispanic women. Individuals from other ethnic groups were not included.
However, this initial study does provide some important insights. It shows how a high calorie diet of fast foods can have long-term effects on body weight and obesity associated metabolic syndrome. Frequent consumption of high calorie foods can set off a perpetual cycle of cravings for similar foods which in turn increase abdominal fat deposits and girth. In this study, participants with greater waist circumference demonstrated higher activation of the reward regions when challenged with high calorie food items. High calorie foods tend to be rich in refined carbohydrates and saturated fatty acids which contribute to an increase in waist circumference, creating a vicious cycle of eating and gaining more weight.
Popular American media have occasionally showcased stories about people who weigh upwards of 500 pounds and their subsequent efforts to lose weight. It is astounding how people can actually reach gigantic proportions before they can come to a decision about tackling this health issue! This study indicates one mechanism that may lead people to gain so much excess weight before they can mentally accept the fact that they are obese and take corrective measures. An individual is likely to spend a considerable period of time being trapped in this vicious cycle of eating the wrong foods, gaining weight and floundering in food choices again before coming to terms with obesity. This study also lends support to the hypothesis that waist circumference and waist-to-hip ratio are better indices for understanding obesity than Body Mass Index (BMI). Body Mass Index also includes weight of limbs which are primarily muscular organs with heavy bones. However, waist circumference and waist-to-hip ratios are a direct measure of abdominal and gluteal fat deposits. Recent research indicates that these metrics may also indicate a predisposition towards unhealthy food choices.
The old saying ‘you are what you eat’ is turning out to be true in so many different ways.
Luo S, Romero A, Adam TC, Hu HH, Monterosso J, & Page KA (2013). Abdominal fat is associated with a greater brain reward response to high-calorie food cues in hispanic women. Obesity (Silver Spring, Md.) PMID: 23408738
Mental Context – A Delicate Subject
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