Being overweight is not harmless – excess fat is the major factor responsible for insulin resistance and resultant type 2 diabetes, and a risk factor for a plethora of conditions including heart disease, stroke, hypertension, high cholesterol, liver disease, gallbladder disease, respiratory problems, arthritis, and infertility.1 Being overweight is thought to be responsible for over 100,000 new cancer cases each year in the U.S. alone, and both overweight and obesity are associated with a greater risk of death from all causes.
Findings in the field of obesity research have given us two more reasons to keep one’s weight in check.
- Excess weight may restrict blood flow to certain areas of the brain, impairing brain function and possibly fueling more overeating.
- Even just a few extra pounds on someone with a “normal” BMI may increase risk of death from heart disease.
1. Brain function
Obesity in mid-life is already known to increase the later risk of dementia, suggesting that excess weight has detrimental effects on the brain.2 The high blood pressure, arterial stiffness, and insulin resistance that come with excess weight could be the factors that harm the brain.
In this particular study, the researchers compared overweight and normal weight subjects (average BMI 28.43 and 21.79, respectively) using an imaging technique that measures blood flow in specific areas of the brain. They focused on the prefrontal cortex, an area of the brain that governs focus, impulse control, and executive function (which includes decision-making, planning, and working toward goals).
In overweight subjects compared to normal subjects, they saw a decrease in blood flow to the brain overall, and also specifically to the prefrontal cortex. Because of the unique functions of the prefrontal cortex in regulating impulse control, they concluded that excess weight has the potential for driving further overeating by reducing blood flow to this area.3
Conversely, another study found that losing weight can improve memory. Subjects underwent memory, concentration, and problem solving tests before and 12 weeks after bariatric surgery. Memory performance had improved after 12 weeks. Importantly, the baseline tests also revealed that the obese subjects and cognitive impairment. Of course, bariatric surgery is not a safe way to lose weight, but this study makes the point that the brain begins to work more effectively when excess fat begins to disappear.4
2. Risk of death from coronary artery disease
Obesity is a known risk factor for heart disease, but a meta-analysis has reported that a little “excess belly fat” can increase the risk of death from coronary artery disease even for people whose body mass index (BMI) is in the normal range. BMI is an imperfect indicator of the health risks associated with obesity, taking only height and weight, and not body fat percentage or fat distribution, into account. Many scientists believe that waist circumference and/or waist-to-hip ratio are better measures of overweight and obesity. Certainly, these are better indicators of visceral fat, which is more metabolically active and thought to be more harmful. Nevertheless, both high BMI and large waist circumference are associated with increased risk of death.
The meta-analysis included data on over 15,000 coronary artery disease patients, and found that those who had “central obesity” (which was evaluated based on waist circumference and waist-to-hip ratio) are at a greater risk of death. This was true not only for obese patients, but normal weight patients as well. In obese patients, central obesity increased risk by 93%, and in normal weight patients by 70%.5
In order to enjoy excellent health, in addition to eating high-nutrient foods, we must also strive to respond appropriately to the signals of true hunger so that we avoid overeating. Too many calories, even from healthy natural foods, will translate into excess fat on the body and therefore health risks.
It should be noted that eating right gives you the ability to lose food addictions and be in better control of your cravings, but food is all around us and people can still overeat for recreation.
1. U.S. Centers for Disease Control and Prevention. Overweight and Obesity: Health Consequences. http://www.cdc.gov/obesity/causes/health.html
2. Fitzpatrick AL, Kuller LH, Lopez OL, et al. Midlife and late-life obesity and the risk of dementia: cardiovascular health study. Arch Neurol. 2009 Mar;66(3):336-42.
3. Willeumier KC, Taylor DV, Amen DG. Elevated BMI Is associated With Decreased Blood Flow in the Prefrontal Cortex Using SPECT Imaging in Healthy Adults. Obesity (2011) 19, 1095–1097
4. Gunstad J, Strain G, Devlin MJ, et al. Improved memory function 12 weeks after bariatric surgery. Surg Obes Relat Dis. 2010 Oct 30. [Epub ahead of print]
5. Coutinho T, Goel K, Corrêa de Sá D, et al. Central obesity and survival in subjects with coronary artery disease a systematic review of the literature and collaborative analysis with individual subject data. J Am Coll Cardiol. 2011 May 10;57(19):1877-86.