According to the Center for Disease Control and Prevention (CDC), more than one third of American adults are obese. The CDC lists stroke, heart disease, type 2 diabetes, and certain types of cancer as “obesity-related conditions.” In 2008, obesity cost the United States an estimated $147 billion in additional medical expenses, and the CDC reports that an obese individual pays around $1,429 more in medical costs than an individual with a healthy weight. 

In addition to a high prevalence of obesity, the United States has a high rate of physical inactivity—around 28 percent of adults didn’t participate in any physical activities in 2014. 

Those hoping to lose weight are faced with a glut of diet regimens, fad workouts, and weight loss programs, many of which require inordinate amounts of time, money, and willpower. ATTN: spoke to Dr. Tim Church, professor at Pennington Biomedical Research Center at Louisiana State University and co-author of “Move Yourself, The Cooper Clinic Medical Director’s Guide to All Healing Benefits of Exercise (Even a Little!)," about what works when it comes to losing weight, and whether it’s really possible to “exercise away” obesity. This interview has been edited for length and clarity.  

Which would you say is more important in terms of losing weight, exercising or eating well? 

Let's just talk about weight in general. There's the not putting on the weight in the first place, which is clearly optimal, because once you've put on weight, your body doesn't want to give it up. I really truly believe physical activity is so important for that. I don't know if it's more important than diet, but it's pretty darn important.

Once you've put the weight on, it becomes an issue of losing the weight. It's not really disputable–clearly, reducing calories has more bang for the buck. Exercise is important, but [losing weight is] probably about 80 percent diet. Crazy enough, after you've got the weight off, people don't lose weight and keep it off unless they're physically active. Once you have lost the weight, then exercise becomes really important for keeping the weight off. For weight loss, I like to say, it's just easier to cut 500 calories out of your diet than to exercise 500 more calories a day every day. 

Do you agree with the idea that each of us have a set point, a weight range of 10 or so pounds, and that it's difficult to maintain a weight below this? 

Once you've put weight on, your body doesn't want to give it up, and that makes sense, because we were designed to hold on to weight to get us through the winter. 

With weight loss, if you've got 20 people, and they all do what I would call world-class behavioral programs, one or two of them are going to lose like 80-100 pounds, and keep it off. And then a whole bunch of them are going to lose 10, 15 pounds. And then a few are going to lose nothing. And what's interesting is, everybody in that group probably pretty much did the same thing. It's just genetics. Some people are wired to slam dunk a basketball. Some people are wired to do super complicated math without even trying. Some people are wired to lose weight. 

And you look at the Look Ahead studies: they've kept weight off people for like 14 years in that study. [When people gain weight back] it's not so much that people go back to their old habits. It's more like people lose touch with the program that got them there. And once you lose touch with the program that gets you there, you're probably going to put the weight right back on. If you don't lose touch, and you maintain those skills, you're actually pretty likely to keep the weight off. It's also pretty clear from the data, you're better off having lost weight and maybe not kept it all off, but kept even some of it off, then you would have been if you'd been gaining weight that whole time. 

What's your opinion on our culture's obsession with dieting? Are there any fad diets you view as particularly dangerous or unhealthy? 

It's not so much dieting. I think it's just weight in general is our fixation. It's very clear now [that] we've got the studies, we've got the data: as long as a diet is relatively reasonable, there's no such thing as a bad diet really. It's more what you're willing to stick with. If you're willing to stick with the paleo more than something else, then bless you, go with the paleo. 

Everybody wants to compare these diets against each other, and the irony is, studies have been done where they compare [diets]....and it made no difference in the amount of weight loss. The only thing that really mattered was how well you stuck to the diet. 

A recent study from the Physical Activity Council revealed that 28 percent of Americans didn't participate in any physical activity in 2014, which is a higher percentage than in 2013. How do you think we reverse this trend?

I think it's a challenge. I think it has to start in the workplace because our workplaces are so important. A) We spend the most hours there, and B) they have so much influence over our schedules in general. I personally think we have to take more of a proactive stance from a workplace perspective, helping people commute to work either via bike or walking, being more flexible on lunch hours, having standing breaks. I don't think it's more treadmill desks, believe it or not. I don't think that's the answer. 

I think it's more helping people be physically active throughout the day. I think it's making it fun. There's a company I work with that Millennials would love called Fitness Interactive Experience. To me that's where the future is: gamification. Where we get people hooked on accumulating steps the way people get hooked on Words with Friends. 

What are your main recommendations for maintaining a healthy lifestyle? 

A few things. One is use it or lose it. I think that's what 20- or 30-somethings don't get; you don't get it until a little bit older. When you're 20, you're sedentary for a month, you go work out a little bit, you get it all back. Mid 30s, early 40s, you can't just all of a sudden get back up from a bad habit. 

[It’s also important to remember] the power of exercise, not just for the hard-earned muscles but for the brain. I don't care what age you are, if you're working really hard, if you're really stressed out, it kind of seems crazy for someone to tell you, "get out and get some exercise," but actually it's probably the best thing you can do. You're going to be more productive and your brain's just going to work better. 

What are the main benefits of exercise for mental health?

It's remarkable. I think I've had over 2,000 people in my exercise studies, and hand to God, I'm amazed at the results of all things mental. Whether it's executive function, whether it's sleep, whether it's anxiety, whether it's depression, whether it's quality of life, the power of exercise in the brain is fascinating. We're starting to get better at understanding it with these fancy imaging studies of the brain we do. We're starting to understand the molecules involved. I don't think we can overstate the benefit of exercise for the brain. 

How much physical activity would you recommend per week? 

If you're a really slow walker, 150 minutes. If you're a fast walker, 100 minutes. If you like to jog and do higher intensity stuff, then 60-70 minutes.