What happens if you exercise but don’t eat well? | CNN (2024)

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Maybe you’re someone who runs 20 to 30 miles a week but regularly gets fast food for dinner. Perhaps you track what you eat Monday through Friday but binge on the weekends. Or maybe you’re someone whose kitchen is stocked with chips, cookies and soda because your workout keeps you thin.

The idea of eating anything you want without consequences might sound like a dream — especially if you’ve convinced yourself that you’re going to burn it off in your next cardio session. But the reality is that it doesn’t matter whether you work out longer or at a higher intensity, experts say. Exercise cannot completely reverse the effects of a bad diet.

You can look thin and still be unhealthy

“Skinny fat” is the unofficial term used on social media to describe a person who looks slim but has a high percentage of body fat. A regular gymgoer could have little subcutaneous fat — the fat right under your skin that’s easy to pinch — but lots of visceral fat. This fat layer is less noticeable because it wraps around your organs.

Visceral fat is dangerous than the outer layer of fat you see, warned Dr. Colin Carriker, an exercise physiologist and associate professor of health and human performance at High Point University in North Carolina. A buildup of visceral fat from eating processed foods high in sugar, salt and carbs could lead to the same type of risks as a person with obesity.

For example, large amounts of visceral fat circulating throughout the body could cause the arteries to harden and become narrower, a disease known as atherosclerosis. This blockage stops blood from flowing to the rest of the body’s tissues and increases the risk for a heart attack and stroke.

Whether you work out longer or at a higher intensity, exercise can't completely reverse the effects of a bad diet, expert say.

There’s also an increased risk for premature death if you exercise but neglect healthy eating. In one of the largest studies to look at the effects of physical activity and diet quality, researchers found those who regularly exercised but ate anything they wanted were at greater risk of mortality compared with people who both exercised and made healthy dietary choices.

Why it’s virtually impossible to outrun a bad diet

If you’re looking to lose weight, the key is to develop a caloric deficit in which you burn calories more than what you are consuming. But eating high-calorie fatty foods regularly can make this a challenge. “You’re overconsuming calories and will have to do way more exercise than a person can sustain on a long-term basis,” Carriker said.

One idea would be to spend more time exercising or engaging in a more intense workout. But this plan doesn’t really work when you’re running on fumes, said Grace Derocha, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. That’s because junk food and sugary beverages are filled with empty calories.

Eating high-calorie foods regularly can make it a challenge to lose weight — even if you spend more time exercising or have a more intense workout.

Processed foods such as soda and candy have little to no nutrients. With a lack of vitamins, protein and fiber to fill you up, it’ll be hard to think about working out when you’re constantly feeling hungry. “People who don’t have a nutritious diet are usually still hungry, moody, and won’t have the same motivation or drive to exercise,” Derocha said.

If you do make it to the gym, those empty calories will make it harder to have a productive workout session. Caroline Susie, a registered dietitian and also a spokesperson for the Academy of Nutrition and Dietetics, explained that fatty foods might give a temporary boost of energy at first, but they wouldn’t be enough to maintain a long or high-intensity workout, making it easier to feel fatigued sooner. On top of all that, any empty calories that aren’t burned off will be stored as fat.

The type of training won’t matter in the long run if you’re not getting the right nutrients. People who are strength training tend to burn more calories than when they do cardio. However, Derocha said that getting nutrients from poor quality foods will make it harder to build muscle mass and fully recover from a strenuous workout.

To build muscle mass, your best bet is to include foods high in protein such as chicken and salmon in your diet. “Macronutrients like protein help build lean muscle mass and sustain it,” Derocha said.

Moderation is key

Being healthy doesn’t mean you have to give up all the foods you enjoy eating. People tend to demonize certain foods, and feeling like you can’t have any sugar or carbs can create a toxic relationship with food, Derocha said.

Instead of feeling guilty for getting takeout last night or for ordering dessert, Susie advised to reshape your perspective. She said to think of food as more than just calories but as the kind of energy it can provide. If you’ve had enough fiber today, look at where you add in extra protein, omega-3s or healthy carbs.

“It’s not good or bad food; it’s just fuel,” she said. “When you look at it from an addition standpoint instead of a restriction standpoint, it’s a healthier approach to fueling yourself.”

Editor’s note: Jocelyn Solis-Moreira is a New York-based freelance health and science journalist.