The reasons why having obesity can cause other diseases or make the ones you have get worse are complicated, but many are related to the chronic inflammation and excess fat that go with obesity. "Really, most major chronic diseases that people have here in the United States and around the world, unfortunately, have a significant link to obesity," Stanford said. Here are some examples of diseases linked to obesity and some reasons for the connection: Heart disease: in people with obesity, an increased amount of blood needs to be pumped through the body to supply enough oxygen and nutrients to tissues. This rise in blood flow puts more pressure on artery walls, resulting in high blood pressure or hypertension. Obesity also leads to atherosclerosis, which is the buildup of fats on artery walls that form plaque, which can break off and cause a heart attack or stroke. Type 2 diabetes: Excess fat around the pancreas affects how it regulates blood sugar. Over time, the pancreas can no longer produce enough insulin. Excess weight also makes cells less sensitive to insulin. That causes insulin resistance, which occurs when your body doesn't use insulin well enough to lower blood sugar levels. Nonalcoholic fatty liver disease (NAFLD): When you have extra fat, some of it can make its way into the liver. "The liver likes to take in fat," explained Stanford. "Imagine a marbleized steak with fat strands throughout it. That's what the liver ends up looking like. The liver can't function with that amount of fat. That's why [NAFLD] is becoming the number one reason for liver transplants," Stanford said. Covid-19: Both obesity and Covid-19 cause inflammation in your body. "We have this kind of perfect storm," Stanford said. "When these inflammatory markers interact with each other … unfortunately, [they are likely to] worsen one's illness and significantly increase one's risk for death," Stanford explained.