Add 10 minutes of exercise to your routine and see the mental results 1:32

(CNN) -- Maybe you're one of those who run between 30 and 50 kilometers a week but eat fast food regularly. Maybe you control what you eat Monday through Friday but binge on weekends. Or maybe you're someone whose kitchen is stuffed with chips, cookies, and soda because your workout keeps you lean.

The idea of eating as much as you want without consequences may seem like a dream, especially if you convince yourself that you're going to burn it off in your next cardio session. But the reality is that it doesn't matter if you train longer or at higher intensity, experts say. Exercise cannot completely reverse the effects of a bad diet.

You may appear thin and still not be healthy

"Skinny fat" is the unofficial term used on social media to describe a person who looks thin but has a high percentage of body fat. A gym goer may have little subcutaneous fat — the fat that's just under the skin and easy to pinch — but a lot of visceral fat. This layer of fat is less noticeable because it envelops the organs.

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Visceral fat is more dangerous than the outer layer of fat you see, warns Dr. Colin Carriker, an exercise physiologist and associate professor of human health and performance at High Point University in North Carolina. An accumulation of visceral fat from eating processed foods rich in sugar, salt and carbohydrates could carry the same type of risks as a person with obesity.

For example, large amounts of visceral fat circulating in the body could lead to hardening and narrowing of the arteries, a condition known as atherosclerosis. This blockage prevents blood from flowing to the rest of the body's tissues and increases the risk of heart attack and stroke.

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Whether you exercise longer or at a higher intensity, exercise can't completely reverse the effects of a bad diet, experts say. (Photo: PersonasImages/iStockphoto/Getty Images)

It also increases the risk of premature death if you exercise but neglect healthy eating. In one of the largest studies on the effects of physical activity and diet quality, researchers found that people who exercised regularly but ate as much as they wanted had a higher risk of mortality than those who exercised and followed a healthy diet.

Why is it virtually impossible to leave behind a bad diet?

If you want to lose weight, the key is to develop a caloric deficit in which you burn more calories than you consume. But regularly eating high-calorie fatty foods can make this challenging. "You're consuming excess calories and you're going to have to get a lot more exercise than a person can sustain in the long term," Carriker says.

One idea would be to spend more time exercising or engaging in more intense training. But this plan doesn't really work when you're at your best, says Grace Derocha, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics. This is because junk food and sugary drinks are full of empty calories.

Eating high-calorie foods regularly can make losing weight a challenge, even if you spend more time exercising or doing a more intense workout. (Photo: Alexander Spatari/RF Moment/Getty Images)

Processed foods, such as soda and sweets, contain hardly any nutrients. Lacking vitamins, protein, and fiber to satiate you, you'll find it hard to think about exercising if you're constantly hungry. "People who don't follow a nutritious diet tend to remain hungry, in a bad mood and don't have the same motivation or desire to exercise," says Derocha.

If you manage to make it to the gym, those empty calories will hinder a productive workout session. Caroline Susie, a registered dietitian and also a spokesperson for the Academy of Nutrition and Dietetics, explained that fatty foods may give a temporary boost of energy at first, but they won't be enough to sustain a long or high-intensity workout, making it easier for you to feel fatigued sooner. In addition, empty calories that are not burned will be stored as fat.

The type of training will not matter in the long run if the right nutrients are not ingested. People who strength train tend to burn more calories than when they do cardio. However, Derocha claims that getting nutrients from poor-quality food will make it difficult to build muscle mass and fully recover from a strenuous workout.

To increase muscle mass, it is best to include protein-rich foods, such as chicken and salmon, in the diet. "Macronutrients like protein help increase lean muscle mass and maintain it," says Derocha.

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Moderation is the key

Being healthy doesn't mean giving up all the foods you love. People tend to demonize certain foods, and feeling like you can't take in sugar or carbs can create a toxic relationship with food, Derocha says.

Instead of feeling guilty about ordering takeout the night before or ordering dessert, Susie advises changing your perspective. Think of food as more than just calories, but as the kind of energy it can provide you. If you've eaten enough fiber today, see where you can add more protein, omega-3s, or healthy carbs.

"It's not about good or bad food, it's about fuel," he says. "When you look at it from an addition standpoint rather than a restriction standpoint, it's a healthier approach to feeding."

Editor's Note: Jocelyn Solis-Moreira is a freelance health and science journalist based in New York.

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