Lifestyle Diseases: Definition & Types

Instructor: Amanda Robb

Amanda holds a Masters in Science from Tufts Medical School in Cellular and Molecular Physiology. She has taught high school Biology and Physics for 8 years.

In this lesson we'll describe what lifestyle diseases are and what makes them different from other diseases. Then, we'll look at three examples in detail: addiction, type 2 diabetes, and cardiovascular diseases.

What Are Lifestyle Diseases?

Picture a yoga studio. Athletic people walk in and out, carrying yoga mats and smoothies. This lifestyle greatly impacts their health and well-being. But, are these people just naturally athletic, so they love yoga, or did they choose to do more yoga, so they became athletic? The same question works in reverse. If a person eats a lot and becomes obese, did they choose to eat more or were they genetically predisposed to obesity?

This is the dilemma surrounding lifestyle diseases, diseases that are not transmitted between people, but rather develop over time due to genetics and personal choices. Today we're going to explore what part of lifestyle diseases are due to personal choices, and what parts are uncontrollable, like genetics.

Let's take a look at three examples: addiction, type 2 diabetes, and cardiovascular disease.

Drug and Alcohol Addiction

Addiction is a disease where an individual becomes physically and emotionally dependent on a substance, like drugs or alcohol. Although drug and alcohol use can be a choice at first, addiction has a genetic component and people can be predisposed to substance abuse. For example, alcoholism tends to run in families. A person with an alcoholic parent is more likely to develop a lifestyle disease of addiction than someone with no alcoholic parents.

Alcoholism tends to run in families

In a lifestyle involving heavy drug and alcohol use, a person's self-care and safety is often sacrificed for getting high or drunk. Different drugs affect different parts of the body. For example, alcohol is processed by the liver into non-toxic compounds that can be excreted. When a person drinks too much, the liver has to work overtime. After doing this for a long time, liver cells start to die and the person develops liver diseases, like cirrhosis, hepatitis, or fatty liver disease.

In all lifestyle diseases, there are controllable risk factors, which are behavior choices that can decrease the risk of the disease, and uncontrollable risk factors, which are genetic and can't be changed. For example, a person who has a known history of drug and alcohol abuse in their family can choose to stay out of situations where drugs and alcohol are used. They can limit their time spent drinking and choose relationships with other people who do not drink. These are risk factors they can control. But, they can't control the fact that their genes predispose them to addiction.

Type 2 Diabetes

Type 2 diabetes is a condition where the body no longer responds to the hormone insulin. The pancreas makes a hormone called insulin in response to high blood sugar levels, which occur when we eat. When blood sugar is high, the pancreas makes insulin, which causes cells to properly store the sugar and keep blood sugar levels balanced. In type 2 diabetes, the pancreas still makes insulin, but the body doesn't respond to it, in a process called insulin resistance. It's like the insulin is invisible to the cells, resulting in dangerously high blood sugar levels.

During insulin resistance the body makes insulin but cells do not respond to it, causing sugar to build up in the blood
insulin resistance

Scientists aren't yet sure what causes type 2 diabetes. However, as with other lifestyle diseases, it's a combination of choices and genetics. Obesity and physical inactivity are both strongly linked to the development of type 2 diabetes. People who hold weight around their middle (also called 'belly fat') are more likely to develop type 2 diabetes than people who have evenly distributed fat. The belly fat produces hormones that can lead to insulin resistance.

Having more fat around the waist is a risk factor for type 2 diabetes
obesity waist size

Lifestyle changes can decrease these controllable risk factors. Increasing exercise and eating a balanced diet with lots of fruits, vegetables, lean proteins, and healthy fats can decrease the risk of type 2 diabetes.

However, there are also some uncontrollable risk factors for type 2 diabetes, which runs in families and has a genetic component. Scientists have found that people with a mutation in both copies of the gene TCF7L2 are 80% more likely to develop type 2 diabetes than people without the mutated gene.

While lifestyle choices, like a poor diet and inactivity, do cause obesity, people's genes also influence how their body stores and metabolizes fat. Some people with an unhealthy diet and no exercise will remain thin and other people who do eat healthy and exercise will remain overweight. Although there is no gene that causes obesity, our genes regulate how we gain, store, and use fat, which can change our weight.

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