By Carel le Roux, MBChB, MSc, FRCP, FRCPath, Ph.D. Member, Nutrition Advisory Board
January 18, 2017
The combination of obesity and aging may have negative effects on the brain. Although more long-term studies are needed, evidence is emerging to support the existence of obesity-related brain changes and increased risk of cognitive aging*.
In a small 2016 University of Cambridge study of 478 adults, lean people had larger brains than obese persons of similar age. Although the findings of the study are interesting, more research is needed to determine why these changes to the brain might be happening and why they might be important to cognitive functioning and overall health.
As the master computer that regulates our vital functions, the brain is also where the causes and solutions to obesity ultimately reside. As an expert in metabolic medicine, I work with a team of medical professionals who are focused on understanding how the “gut talks to the brain” and how these signals can be optimized to improve health.
But exactly which part of the brain is responsible for obesity? Many think it’s about willpower and that patients who are obese have a lack of discipline. However, it’s actually the sub cortical areas of the brain, such as the hypothalamus and nucleus tractus solitaries, controlling our vital functions including hunger and fullness. When we look at where the hypothalamus is situated, we see that it does not have that much contact with the areas of the brain we use for philosophy or mathematics, also called the cortical areas. For that reason, it is difficult for somebody to “think” his or her way to thin.
When most of us are offered a choice of dessert between broccoli and a more palatable piece of cake, we will almost always select the second. So why do we choose the cake when it isn’t more nutritious than broccoli? Because taste overrides nutritional content. To understand the underlying mechanism, we have to go to functional Magnetic Resonance Imaging (fMRI) studies, which use pictures to determine which part of the brain receives the most blood flow when viewing a palatable food. The reward system is activated when palatable food pictures are shown to normal and overweight people. We can then see which reward centers in which specific parts of the brain receive more blood flow when a picture of palatable food is shown.
For an example to illustrate the importance of taste, just look at patients who have had surgical treatments for obesity including gastric banding and gastric bypass. These patients have their operations on their stomachs and lose a quarter of their weight, but often they come back to clinic and ask, “Doctor, where did the surgeon operate? Did she operate on my stomach or did she operate on my head, because all the signals that I now receive are actually in my head?” When we investigate patients after gastric bypass with fMRI and pictures of palatable foods, we see a reduction in their reward centers. The operation on the stomach changed the way the brain is responding to the visual cue of palatable food. This explains why patients after bariatric surgery eat less food and specifically less calorie-dense foods, as specific areas of the brain involved with appetite and reward are down regulated.
The Importance of a Healthy Diet
To help promote brain health, individuals of all ages should get a balanced diet consisting of fiber, micronutrients (vitamins, minerals), macronutrients (protein and fats), phytonutrients (plant compounds) and plenty of water. This is what the Herbalife Global Nutrition Philosophy advocates. Specifically, it calls for:
- Up to 30 percent fats from food and supplements including omega-3 fatty acids and by limiting saturated fat
- 40 percent carbohydrates with 25g of fiber
- 30 percent protein
*IOM (Institute of Medicine). 2015. Cognitive aging: Progress in understanding and opportunities for action. Washington, DC: The National Academies Press.