7 exercise myths debunked

You’ve heard it before: exercise can replace a bad diet or crunches give you six-pack abs. Such “gym-talk” has led to many common myths about the dos and don’ts of exercise.

But this fact remains clear – exercise is one of the best things you can do to lower your risks for many cancers. This includes colon, breast and endometrial cancers.

Regular exercise can help you maintain a healthy weight, reduce stress and strengthen your immune system. It also curbs your risk of diabetes and heart disease.

So, we asked MD Anderson senior exercise physiologist Carol Harrison to bust the most common exercise myths to help you get in shape.

Here are Harrison’s top seven myths. 

1. Myth: You can target your fat burn. 

Truth: Working out can reduce overall fat, but you can’t control what part of your body burns the most fat.  “Your body breaks down fat and uses it as fuel when you exercise,” Harrison says. “But your body’s not picky. It’ll burn fat from anywhere in your body, not just the part you’re working the most,” Harrison says.

2. Myth: Lifting heavy weights bulks up women. 

Truth: Lifting weights tones and shapes your body – it doesn’t make you look like a bodybuilder. Women have low levels of testosterone so they don’t naturally build massive muscles, Harrison says.  “There is nothing wrong with a woman pushing up to 200 pounds on a leg press if she can do it.”

Lifting weights can prevent loss of muscle mass, help build bone density and increases the rate at which your body burns calories to keep you at a healthy weight. Maintaining a healthy weight can help you fight off diseases like cancer.

3. Myth: Crunches are the best moves for your core. 

Truth: “Crunches are one of the least effective core exercises because they don’t get rid of belly fat,” Harrison says. To shed the extra jiggle, increase your cardio workouts and add resistance training that targets the entire core.

It’s important to trim excess belly fat because it can increase your chances of getting heart disease and certain cancers. It also puts you at risk for metabolic diseases like diabetes.

4. Myth: Exercise can erase a bad diet. 

Truth: “Exercise by no means makes up for a bad diet,” Harrison says. Diet and nutrition play a larger role than exercise in weight management and cancer prevention.  In fact, some foods actually help protect you against certain cancers.

So, don’t treat exercise like an activity that justifies eating unhealthy foods.

5. Myth: When you stop strength training, muscle turns to fat. 

Truth: Muscle can’t turn into fat, just as fat can’t transform into muscle. “Fat and muscle are two different types of tissue,” Harrison says. When you stop strength training, you lose muscle mass and your metabolism slows down.  A sluggish metabolism means your body is burning fewer calories at rest, which can lead to weight gain.

Being overweight or obese increases your risks for colon, pancreatic, kidney, endometrial, gallbladder, esophageal and breast cancers.

6. Myth: You need to spend hours in the gym. 

Truth: You can get all the benefits of exercise whether you’re at the gym or at home, says Harrison. The key is to exercise smarter, not longer. To get the most out of your workout, strength train before you do aerobic exercises.

Here’s why:  When you work out, your body activates its limited supply of carbohydrates first. This is the best fuel for short term and intense exercise, like strength training. After your body has depleted its carbohydrate storage, it starts using fat for fuel. And fat is the best fuel for aerobic exercise.

You should aim for at least 150 minutes of moderate physical activity, like brisk walking and slow swimming, each week to reduce your cancer risks. Or you can do more vigorous activities, like running and fast bicycling, for at least 75 minutes each week. 

7. Myth: Stretch before exercising.  

Truth: It’s more effective to stretch after you exercise when your muscles and joints are warm. “Stretching before has little to no benefit,” Harrison says. Stretching after can improve performance and flexibility, and helps you maintain a healthy range of motion in your joints.

Stretching also can reduce stress, decrease muscle tension, and improve your circulation and posture.

“The more fit you are, the better chance you have to fight off diseases like cancer,” Harrison says. “So, focus on the true dos and don’ts of exercise, and get moving.”  

Request an appointment at MD Anderson's Lyda Hill Cancer Prevention Center online or call 877-632-6789.