The Role of Inflammation in Obesity
The Role of Inflammation in Obesity
Joy Stepinski, MSN, RN-BC
May 4, 2025
Over the past few months, we have looked at the implications of obesity and the significant effect of diet on weight. Foods common to the Western diet often contribute to chronic disease, including animal-based, highly processed, and high-fat foods. One way a high-fat diet negatively affects the body is due to complex mechanisms that cause chronic inflammation, which is a key trait of obesity. As we will see, chronic inflammation profoundly affects the human body.
Inflammation is normally essential to homeostasis, the balance the body constantly seeks to achieve, maintaining important functions. During an injury or infection, inflammation is crucial in helping the body protect against unwanted pathogens, repair tissue, and restore balance [1]. Yet in obesity, chronic inflammation causes a loss of this important regulation, disrupting homeostasis.
White adipose tissue stores energy and regulates certain metabolic functions [2]. Metabolism describes the process by which the body breaks down nutrients to use for energy. Regulating inflammation is one of the functions of adipose tissue. Certain molecules are released that contribute to or inhibit the inflammatory process.
In obesity, fat cells enlarge and change shape in response to improper nutrients. As a result, the blood that supplies the fat cells is reduced. The tissue consequently experiences insufficient oxygen, disrupting the important balance within the body. Pro-inflammatory molecules initiate the inflammatory response, including the increased production of pro-inflammatory adipocytokines. Adipocytokines are proteins secreted by adipose tissue involved in cell signaling and metabolic regulation. The increase in proinflammatory molecules causes a change in the blood vessels. Chemokines recruit immune cells into adipose tissue. Adhesion molecules are produced that cause immune cells to adhere to the blood vessel lining. As a result, fluid and cells move out of the blood vessel into the surrounding tissue more easily, potentiating inflammation [3]. Inflammation is two-fold. Locally, macrophages and T cells lead to chronic inflammation within adipose tissue. Once the inflammatory signals travel into the surrounding tissue, a systemic response ensues.
Macrophages are immune cells that play a role in the body’s defense system by engulfing pathogens and secreting proinflammatory molecules. This response can contribute to a chronic state of inflammation. Factors like the lack of cellular oxygen, excessive nutrient intake, lipid accumulation, oxidative stress, and dysfunctional fat metabolism stimulate the production of adipocytokines [5]. These biological substances affect the metabolic regulation of the pancreas and liver. Consequently, conditions like type 2 diabetes and fatty liver disease develop. Proinflammatory molecules (i.e., TNF-α and IL-6) can interfere with insulin signaling by activating inflammatory responses that disrupt insulin receptor function. Insulin receptors are like gates on the cell surface that allow the entrance of blood sugar into the cell. In type 2 diabetes, insulin resistance impairs the transport of blood glucose into the cell for energy use.
Along with macrophages, T cells accumulate in adipose tissue. T cells are lymphocytes, a white blood cell that recognizes foreign molecules (antigens) [6]. They are produced in the thymus gland. In an immune response, a macrophage first responds to the antigen and presents it to the T cell. The T cell can destroy the antigen or release lymphokines that activate more macrophages while stimulating B cells to produce antibodies. Some T cells can potentiate inflammation in obesity. T cells influence the recruitment of inflammatory cells to adipose tissue, changing insulin sensitivity. Leptin (a pro-inflammatory adipocytokine) promotes T cell activation, further causing chronic inflammation and insulin resistance.
The inflammatory response in obesity has been linked with many chronic diseases, including type 2 diabetes and fatty liver disease, discussed above. According to one retrospective study of 420,636 Canadian adults, other conditions include cardiovascular disease, chronic pulmonary disease, rheumatoid arthritis, chronic kidney disease, multiple sclerosis, peripheral arterial disease, alcohol use, depression, constipation, psoriasis, cancer, and more [7]. Chronic disease directly impacts quality of life and well-being, including mobility, pain, fatigue, emotional health, and overall longevity.
Chronic low-grade inflammation in obesity contributes to metabolic syndrome, characterized by three of the following conditions: high triglycerides, high cholesterol, high blood pressure, high blood glucose levels, and abdominal obesity [8]. Metabolic syndrome significantly increases the risk of diabetes and cardiovascular disease, which may lead to heart attacks, stroke, heart dysrhythmias, and obstructive sleep apnea. The immune response triggered by inflammation further affects organs, such as the liver, heart, and kidneys, worsening overall metabolic function.
Recent Chinese research of 59,927 subjects [9] demonstrates that metabolic syndrome, when combined with chronic low-grade inflammation, significantly increases the risk of cancer. Those with a higher CRP level showed higher incidences of breast, endometrial, colorectal, kidney, and liver cancers. Other diseases that are related to obesity include degenerative joint disease, asthma, pulmonary embolism, gallstones, polycystic ovarian syndrome, preeclampsia and eclampsia in pregnancy, infertility, urinary stress incontinence, and poor wound healing [10].
The skin is the largest organ of the body, and is directly impacted by excess weight and inflammation. Notable conditions include stretch marks, darkened patches in skin folds (acanthosis nigricans), skin tags, rough red bumps (keratosis pilaris), facial acne, puffiness due to fluid buildup, infections in skin folds, swelling and sores of the lower legs, excess abdominal weight, and increased sweating. Other skin conditions include psoriasis, cellulitis, and melanoma [11]. As a result, body image issues are common.
Interestingly, research suggests that the human body has different types of fat. While white adipose tissue is related to inflammation, brown adipose tissue is anti-inflammatory. Located around the neck, collarbone, and along the spine [5], brown fat is activated during exposure to cold and is inversely related to body mass index (BMI). Among its roles are burning energy for heat production and releasing a batokine hormone that promotes fat burning in the liver [5]. Mitochondria, the organelles found within cells that aid energy production, give fat its brown color. Exercising, regular exposure to cold, a nutritional diet, and adequate sleep increase brown fat reserves [4]. People with lean body weight have more of this type of fat than obese individuals [5]. Brown adipose tissue is also depleted in those with fatty liver, obesity, and type 2 diabetes [12].
Studies show that nutrition plays a large role. In a large cross-sectional study using data from the National Health and Nutrition Examination Survey (NHANES) [13], information from 27,915 participants was examined with an 11.2-year follow-up. The study looked at diet quality through a healthy eating index (HEI) and the level of C-reactive protein, a marker for inflammation. Results concluded that “increased intake of a healthy plant-based diet was associated with lower inflammation…and may also benefit individuals with obesity who had low and moderate inflammation” (p. 2723).
A separate British study published last month investigated the role of fiber and protein in inflammation. The research included 128,612 subjects. Results showed that high dietary fiber and vegetable consumption were associated with a normal body mass index (BMI), while those with low fiber and animal food intake had higher obesity. High fiber had an inverse relationship with CRP [14], or inflammation.
Ultra-processed foods have been scrutinized in the health literature. Known as the “cornerstone of the Western diet,” they are cheap, palatable, and widely available in a ready-to-eat state [15]. However, many highly processed foods lack nutrients. Instead, they are energy-dense with saturated fat, added sugars, and sodium. Additives and chemicals allow for a long shelf life. Processed foods may wreak havoc on the gut microbiota, causing chronic inflammation. Microbes that normally protect the gut are displaced, which can cause a leaky gut, thereby allowing toxins and bacteria to enter the bloodstream. Mechanisms suggested are a low intake of anti-inflammatory foods (fruits and vegetables) and fiber. Sufficient fiber intake helps maintain low CRP levels and gut homeostasis. Additives and chemicals may disrupt the proper functioning of hormones, causing disease development, such as cardiovascular disease, diabetes, and obesity.
The food we feed our bodies plays a vital role in overall health. The average human consumes approximately one ton of food annually. Insufficient nutrients and fiber have detrimental effects. Some actions to consider are: eliminating highly processed foods from the diet, limiting meats to organic or wild-caught animals 2 – 3 times per week, and prioritizing fiber-filled foods. These include complex carbohydrates, such as whole grains, corn, potatoes, and legumes, as well as fruits and vegetables. While diet is an enormous factor, other components influence inflammation in obesity. We will examine these in the future.
As we have seen, the role of inflammation in obesity greatly affects well-being, quality of life, and longevity. Low-grade chronic inflammation resulting from excess weight can lead to grave health concerns. Addressing obesity through proper nutrition is a key step in decreasing weight and inflammation.
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