For many years, it’s been understood that obesity triggers a chronic, low-level inflammation throughout the body, which leads to various health problems like type 2 diabetes, high cholesterol, heart disease, and even brain-related issues. Interestingly, the brain plays a significant role in this process by regulating our appetite and metabolism. Genetic factors also play a role, with many obesity-related genes affecting brain function easy access to foods with unhealthy and high-calorie foods not only affects a person externally but also has internal consequences. Research has found the hypothalamus becomes inflamed. This inflammation disrupts the brain’s ability to regulate energy balance and contributes to insulin resistance, making it harder for the body to manage blood sugar levels. The hypothalamus plays a crucial role in regulating our metabolism and appetite, it contains different types of signals such as leptin and insulin which regulate our food intake. When a person consumes a high-fat diet, the hypothalamus is triggered and doesn’t respond as well to insulin and leptin, which are both hormones that regulate sugar and control appetite, saturated fatty acids interfere with normal signaling of insulin and leptin which then leads to positive energy balance and weight gain, the inflammatory pathways in the hypothalamus become activated leading to insulin and leptin resistance. This resistance leads to weight gain and other metabolic issues.2 Leptin, as we know, regulates appetite and energy balance, when you eat a high-fat diet it leads to an increase in fat stored in the body, which then turns to higher levels of leptin being released in the bloodstream, leptins role is to tell our brain to eat less and burn more energy which then helps us maintain a healthy weight, when a person consumes a high fatty diet this leads to leptin resistance, even though the brain levels are high the brain becomes less responsive to its signals when the body becomes resistant it doesn’t do a good job in telling the brain to eat less, which can lead to more eating and weight gain.3 When a person eats a lot of high fatty diet this can make cells less sensitive and when the cells don’t respond the body makes insulin to try to compensate for it, however over time this can mess up how the body controls hunger which makes a person want to eat more high fatty foods.1 TNF-α is a protein that responds to inflammation or infection, it promotes leptin and insulin resistance by activating certain signaling pathways. When the central nervous system is exposed to low levels of TNF- α this can impair leptin and insulin function in the hypothalamus. TNF- α also increases the production of PTP1B which is a protein that that negatively regulates insulin and leptin signaling. Elevated levels of PTP1B, particularly after long-term high-fat diet consumption, impair insulin signaling by directly inhibiting key molecules involved in the process. Deleting PTP1B specifically in neurons has been shown to improve metabolic health and reduce weight gain.
1 Ilyas, Athif, et al. “The Metabolic Underpinning of Eating Disorders: A Systematic Review and Meta-Analysis of Insulin Sensitivity.” Molecular and Cellular Endocrinology, Elsevier, 28 Oct. 2018, www.sciencedirect.com/science/article/abs/pii/S0303720718302867.
2Jais, Alexander, and Jens C Brüning. “Hypothalamic Inflammation in Obesity and Metabolic Disease.” The Journal of Clinical Investigation, U.S. National Library of Medicine, 3 Jan. 2017, pubmed.ncbi.nlm.nih.gov/28045396/.
3Mendoza-Herrera, Kenny et al. “The Leptin System and Diet: A Mini Review of the Current Evidence.” Frontiers in endocrinology vol. 12 749050. 24 Nov. 2021, doi:10.3389/fendo.2021.749050
