The fight against weight gain and fat loss is something many people are fighting globally. Understanding that losing weight is more than simply being a smaller size is still foreign to many people, causing them to adopt unhealthy habits. When you lose weight, one needs to make sure they are eating appropriate foods because what you eat could have a huge impact on your health, sometimes even more than the weight itself. Obesity is known to increase the risk of many cancers and weaken our body's ability to fight tumors. In a 2019 study obesity was linked to 4.8% of new cancers in men and 10.6% in women. But a new study shows that not all fats are the same when it comes to this risk. The type of fat we eat can have a big impact on how tumors grow, even if a person is the same weight. How Do Different Kinds Of Fat Affect Tumor Growth? Researchers wanted to understand if all fats are the same when it comes to cancer risk in people with obesity. They fed mice different high-fat diets and found some surprising results. Diets made with animal fats like lard, beef tallow, and butter made tumors grow much faster. However, diets made with plant oils like coconut, palm, and olive oil did not cause this accelerated tumor growth. What's most important is that all the mice were equally obese. This shows that the type of fat, not just being obese, is what made the difference in how the tumors grew. How Did These Fats Affect Our Immune System? The researchers discovered that the type of fat in the diet affects the body's immune system, specifically two types of cells: natural killer (NK) cells and CD8 T cells. These are the "killer" cells of our immune system, responsible for fighting off cancer. In mice fed the butter-based diet, these immune cells were less active and fewer in number inside the tumors.In mice fed the palm oil-based diet, these immune cells were more active and better at fighting the tumors.This difference seems to be related to a specific fat-related molecule. The butter-based diet led to a buildup of a fatty substance called long-chain acylcarnitine in the blood. This substance acted as an "immunosuppressive metabolite"—it actively suppressed the function of the CD8 T cells, making them less effective at killing cancer cells. Can Obesity Cause Cancer? According to the National Cancer Institute, a strong connection between excess body weight and at least 13 types of cancer has been found. The risk is highest for endometrial and esophageal cancers. For these, a person with severe obesity can have a risk that is 5 to 7 times higher than someone at a healthy weight. For other cancers, the risk for people with obesity can range from a 10% increase to double the risk. Why Does Excess Weight Increase Cancer Risk? Scientists have several ideas about how obesity and overweight can lead to cancer: Extra Estrogen Fat tissue produces more estrogen. High levels of this hormone can increase the risk of cancers like breast, endometrial, and ovarian cancer. Insulin and IGF-1 People with obesity often have higher levels of insulin and a hormone called IGF-1 in their blood. High levels of both can encourage cancer growth, especially for colorectal, thyroid, breast, and other cancers. Chronic Inflammation Excess body fat can cause ongoing, low-level inflammation in the body. This inflammation can directly help tumors grow. Hormones from Fat Cells Fat cells release hormones called adipokines. Some of these, like leptin, can promote cell growth, while others, like adiponectin, which helps protect against cancer, are less common in people with obesity. Does Losing Weight Lower Cancer Risk? While more research is needed, some studies suggest that losing weight can reduce the risk of certain cancers. In one large study of postmenopausal women, those who lost more than 5% of their body weight had a lower risk of obesity-related cancers, especially endometrial cancer. Weight loss surgery (bariatric surgery) has also been shown to reduce the risk of cancer overall, especially in women. Some newer weight-loss medications have also been linked to a reduced risk of certain cancers.