How the Brain Controls Weight

The brain plays a central role in the regulation of weight. There are two systems within the brain that play a large role in the regulation of weight and maintenance of weight stability. These systems are:
• The Hypothalamic “hunger” system [Homeostatic network]
• The Mesolimbic “reward” system [Hedonic network]

Let’s explore the hypothalamic system first. The ‘hunger system’ is comprised of the brain, nerves, gastrointestinal tract, fat, liver and muscle cells as well as numerous hormones. This system is constantly communicating and receives feedback from the body in regards to energy stores and energy input (food). It works to maintain weight and aggressively resists weight loss. The hormones commonly associated with this system include Ghrelin, Peptide YY (PYY), Glucacon-like peptide 1 (GLP-1), Cholecystokinin (CCK), Leptin and Insulin.  These hormones work within the homeostatic network to promote hunger or satiety (fullness) depending on whether the body needs more calories or whether the energy stores are sufficient. This all happens subconsciously and is mostly determined by your genes.

The second system is known as the hedonic ‘reward’ system and drives food intake through behavioural responses based on the reward, or enjoyment, pathways in the brain. These pathways have a close connection to the prefrontal cortex of the brain which integrates sensory information such as sight, taste, touch, sound and smell. This system can override the hypothalamus and even during the “fed/energy balanced” state, can promote food intake for the purpose of achieving reward sensations. This is why when we see our favourite foods, even when we aren’t hungry, we like to eat and enjoy those foods.

Both pathways communicate with each other and strongly resist weight loss. If weight loss is achieved the body will increase hunger drive and decrease energy expenditure in an attempt to return the body to it’s “set point.” This is why losing weight and maintaining weight loss can be so difficult.

Medical science has discovered ways to override these pathways and we now have treatment that can help a person to lose weight and maintain that weight loss. We can interrupt these pathways through bariatric surgery and weight loss medications/injections. Your MedSurg Weight Loss Doctor can help you to discover which intervention may be right for you.