The Brain & Environment Regulate Weight
Losing weight and successfully maintaining it over the long term is not as much about what you put in your stomach; it’s more about what’s happening in the brain and your environment.
Increased prevalence of obesity (over 40% of the population in the US has obesity) isn't primarily due to weak willpower, inaccurate calorie counting, proximity to McDonald's, or too much sugar in the diet. You can put most of the blame on our prehistoric brain seeking survival in our modern world. The Energy Balance Model (EBM) of obesity posits that the brain regulates weight mainly below our conscious awareness (subcortical) by controlling food intake. Our brains are attracted to energy-dense rewarding foods. For many people, food's sensory/reward aspects simply overwhelm the satiety and appetite signals. Our brains haven't changed much since our ancestral hunter-gather days, however, our food environments have become rife with high-calorie ultra-processed convenient foods that require little energy expenditure for humans to access.
The vast majority of us are no match against the teams of neuroscientists, chemical engineers, marketers and chefs that make, advertise and package our food. Much of it is designed to overcome our biology and get us to eat more. Billions of dollars are spent every year trying to figure out how to get humans to buy and consume more food.
Over the past several decades, many changes in the food environment have led to increased food intake and obesity prevalence. The prime suspects include:
Availability of a wide variety of inexpensive food
Ubiquitous marketing of food and exposure to food cues
The prevalence of convenient, palatable energy-dense foods
Larger portion sizes
Increases in sugar, fat and salt in many foods and less protein and fiber
The rise of ultra-processed foods
Stress/boredom induced overeating
Habit driven food intake
NOTE: On the individual level, detailed mechanisms by which our food environment alters brain circuits controlling food intake and why some are more susceptible to obesity remain unclear. However, on the macro level, gene-environment interactions clearly explain the worldwide escalation in obesity, whereby rapid changes in food supply and environment trigger overeating coupled with our increased sedentary behaviors. In the words of one group of researchers, humans have “fat brains and greedy genes.”
Different diets can result in markedly dissimilar internal signals (e.g., circulating hormones and fuels) that influence food intake and metabolism. Thus, the EBM does NOT postulate that all calories are metabolically alike inside the body. The EBM acknowledges that the quality and composition of the diet and the food environment are essential in preventing and treating obesity and explains why “eat less and move more” is ineffective advice. This popular guidance is equivalent to telling individuals suffering from depression to 'snap out of it and be happy.'
The EBM acknowledges that different food environment factors and diets can lead to obesity in disparate individuals. Thus, the need for highly individual nutrition approaches for managing weight. Not everyone should necessarily be on a low carb or low-fat diet! One size does not fit all. Trial and error is an essential strategy in finding which diet works best.
Findings from brain functional magnetic resonance imaging (fMRI) studies have consistently associated obesity with an increased motivational drive to eat, increased reward responses to food cues and impaired food-related self-control processes. For most people, in the presence of delicious foods, the brain’s reward circuitry overwhelms the satiety signals. For our great ancestors, on the plains of Africa, overeating had adaptive value. However, in modern societies, where food is widely available, this adaptation has become a liability. We are descendants of the people who 'overate' and were successful at storing fat. These humans lived through famines and times of hunger. It has only been since the rise of our omnipresent obesogenic environment that overeating has become maladaptive.
The brain reward circuitry that evolved over the last 2 million years has resulted in many humans being more responsive to environmental food cues than they are to homeostatic stimuli. Unfortunately, data show some people are more susceptible than others.
We have plenty of data noting that weight loss is not about one specific diet or one particular exercise program. What seems more important is finding an individualized approach that creates the necessary dietary and activity change and helps you develop permanent behavioral tools and a supportive lifestyle. This is the way.