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The world is in the grips of an obesity epidemic. The UN’s Food and Agriculture Organization warned last year that “adult obesity is rising everywhere at an accelerated pace.” Some 640 million adults worldwide are now considered obese, or roughly 13 percent of the global adult population.

As part of our Expanding Nutrition Frontiers webcast series, eCornell’s Chris Wofford was joined by professor David Levitsky from the Division of Nutritional Sciences at Cornell University to discuss why so many of us are putting on extra weight and what can be done about it.

Wofford: David, we’ll get into the solutions later but let’s start by talking about the problem. What is age-related weight gain? What is happening physiologically?

Levitsky: Well, I think age-related weight gain is perhaps the most serious medical problem in our country and maybe the world. Age-related weight gain is weight gain that occurs after you stop growing vertically. So after about 18 years of age, you continue to gain weight without growing taller. That age-related weight and the rate at which you gain the weight are the best predictors of whether you’re going to suffer from diabetes, hypertension, heart disease, stroke and many kinds of cancers.

Wofford: I was doing a little bit of research before this and I read that our muscle fiber tissues begin to disappear to some degree and get replaced with fat. Is there a biological reason for that?

Levitsky: Well, the decrease in muscle mass really doesn’t occur until middle age, your 50s or 60s. And it’s not that the muscle is replaced by fat, we’re just adding fat. Most of that weight gain is due to the fact we consume more calories than we expend. Simple as that. Despite all the hundreds of diet books out there teaching all kinds of magic, it is simple energetics.

Now we can ask why we are consuming more calories than we expend… My colleagues and I agree that we live in an environment in which we are surrounded by signals that make it easy. In psychology, we call this priming. So if we see food, it actually makes us want to eat. And we have experimental data showing that if you see people eating, you want to eat. When we see a television commercial containing food, we’ll get up and go to the refrigerator to get something to eat. We are totally surrounded by these stimuli and what is referred to as an obesogenic environment.

It’s obesogenic because simply responding to all the stimuli in the environment causes us to gain weight. And that’s the reason we’re gaining weight as we get older. We’re subjected to more and more of these stimuli and we’re going to respond by eating just a little bit more than we expend.

Wofford: Let’s back up a little bit and talk about your experience as it relates to psychology and nutrition, and the experiment that you conducted several years ago related to weight gain and how it might be prevented.

Levitsky: Okay. This all started for me when I was sitting in my office and I had someone pop in and say that they wanted to study “the freshman 15”, which is the idea that college students gain around 15 pounds during their first year. It turns out it’s less than that – more like 5 pounds – but the problem is real. Nobody was really studying it so I said, “Okay, go ahead and look at it.”

So we gave freshmen scales at the beginning of the semester, had them weigh themselves at the beginning the semester and again at the end of the semester, and by then they had gained about 5 pounds here at Cornell. We didn’t really believe it was real, so I got very excited about these findings because it represented an opportunity to study techniques to try and prevent that weight gain.

The most logical way to lose weight is to say, “I’m just going to reduce my calories by 200 per day.” Diets have been around forever, and forever they’ve shown that they don’t work for the vast majority of people.

They’re still responding to the stimuli in their environment and it gets more and more difficult the more weight you lose. So the traditional way of concentrating on caloric intake fails.

Wofford: Nothing new there. Okay, so you’re doing this study and discover that the freshman 15 – or maybe the freshman 5 – is real. What’s next?

Levitsky: My training is in psychology and it’s in a certain kind of psychology called behaviorism, which is a discipline that’s simply dedicated to your behavior in certain situations. In order to change behavior, you have to have some monitor of that behavior. When it comes to weight, that monitor can simply be stepping on a scale.

So the first thing we tried was to give freshmen scales and ask them to weigh themselves every day and keep a graph of their weight. We found that those who followed through and weighed themselves did not gain weight while those who didn’t follow through gained two and a half kilos. I did not believe it the first time we did the experiment so we replicated it the following year and the results were very clear: those who weighed themselves every day and had a record of their weight in the form of a graph do not gain weight.

But of course, college students do not represent the population so we then used older people at a health center for a two-year study and again, those who continually monitored themselves actually lost weight.

Now we have a project that we’ve just started here at Cornell, working with the staff because neither students nor people who belong to a health club are representative of the population. We’ve recruited staff from the groundskeepers to the police force here — wherever we could find real people who are more representative of the population — and half of them have scales and half of them do not. We weigh everybody at the beginning and we weigh everybody at the end. Our hypothesis is that people who weigh themselves regularly won’t see a weight gain. We’ll have to wait and see how it turns out.

Wofford: What is happening from a behavioral psychology standpoint? When they look at this weight graph, what is happening in their minds? How does that affect what they do?

Levitsky: Well, there are actually three hypotheses that we have been entertaining as to how this works. The first is that it is simply having the information. They look at the scale and say, “Oh, 155 pounds is too much for me.”

A second possibility is that it works as reinforcement. If you see yourself losing weight, you say, “Oh wow, that makes me feel good” and then you are going to reinforce those behaviors that made you lose weight. That is also a possibility but I’m not holding my breath that either one of these two hypotheses will work.

I prefer to consider the third hypothesis, which is based on priming. Just like when you see food and it makes you want to eat that food, we are working on a priming idea where just stepping on a scale is a primer for all the health information that you already know. You know what to eat, you know how you should behave but you need something to stimulate you. I think that is what happens on the scale.

We have done a number of studies in our laboratory where we bring people in for a focus group. Well, we tell them it is a focus group, but it’s not really. We put snack food in front of them and then sometimes we show them advertisements for cars or how beautiful it here is in the Finger Lakes and sometimes we show them food commercials. When we show them the food commercials, they consume considerably more than if we show them a food-neutral stimulus.

But when you have them weigh themselves just before they go in – we don’t tell them anything about why we’re weighing them, we just get their weight – they consumed considerably less.

Wofford: Even though they’re exposed to the same amount of stimuli.

Levitsky: Right, the stimuli is the same but stepping on that scale changes the way you react to things.

Wofford: I’d like to turn to the audience and get them involved. We have a question here from Christine, who says, “I have been stepping on the scale every day for years and I run three to four miles three times per week and yet I have gained at least 10 pounds.” Is this where we get into the issue of the quality of the calories?

Levitsky: Well, stepping on the scale does not produce magic. It should be a means of informing you of where you are. If she’s gained ten pounds over a few years, she can reverse it by making changes to her eating. You have to change something. If you can live without desserts, without snacks or with smaller portions, these are all good techniques to cause that negative energy balance to get you to lose weight. The only thing I would warn her is try not to lose that ten pounds overnight. She has to think of it in terms of a slow return back to her weight and she can do it. I mean, running 10 to 15 miles is no small thing.

Wofford: I’ve got a question here from Marsha. She says, “I weigh myself every day and work out at the gym every day but I could also use a calorie counter app on my phone. I feel like keeping track of the calories is the most influential in my weight control.”

Levitsky: Calorie trackers work but the problem with the trackers, whether it’s movement trackers or diet trackers, is that most people can’t keep that up for long periods of time. People don’t have room for extra things in their lives and inputting that information is an extra thing. That’s why I tell people in our studies to put their scale right by their bed. You get out of bed and step right on that scale and it takes two seconds to get a measurement, but it’s nothing extra you have to add into your life.

Wofford: Erica asks: “Do you believe that weight loss is about 80 percent of what you put in your mouth and 20 percent physical activities?” Is this a common metric?

Levitsky: There are a lot of reasons why people should exercise. However, and I hate to tell you this, exercise has very little effect on what you weigh. The reason is that the body is so efficient that when you go out and spend that energy and then come back and rest, your metabolic rate after you rest actually goes down lower than it would have had you not exercised. So, exercise doesn’t benefit your weight. It does, however, benefit your risk of heart disease, the prevention of diabetes, and the prevention of stroke and cancers.

Wofford: OK, so exercise isn’t going to get you there. It’s all about what you eat?

Levitsky: I strongly recommend that if you try to lose weight, it should be done very slowly. You should lose weight probably at no greater than one percent decrements. So you see what your weight is and then set a goal for a weight at no more than one percent lower than that for whatever time period you need. You need to take it one step at a time. Some people could do it immediately, while for others it will take them a while to figure out that maybe they can’t live without that afternoon snack. And that’s fine. You just try something else like lowering your portion sizes or skipping dessert. You figure out what works for you and then you try to get to that lower value. Once you discover you can live with whatever change you made, then you make another change. You go down another one percent.

I don’t recommend that anybody get below 10 percent weight loss. At 10 percent, you can reverse things like diabetes and lower blood pressure. All of the beneficial effects of weight loss occur at a maximum of about 10 percent weight loss. That’s all you need in order to improve your health. Now, if you want to lose it for other reasons, aesthetic reasons or whatever, that’s another matter.

Wofford: Another question from the audience focuses on so-called good calories versus bad ones. Do you have any thoughts on this?

Levitsky: Healthy food will do the most to reduce your caloric intake. Low fat foods will clearly decrease your caloric intake. If you reduce the portion size, you’ll be satisfied with less food. If you can do without the potatoes, without the the carbs, fine. Are there good carbs, bad carbs or good calories? It makes a great title for a book, but the nutritional science says that a calorie is a calorie.

Wofford: We’ve discussed weight solutions for individuals but is there anything we can do as a society to address this problem?

Levitsky: I think the scale is the most healthy tool that you can use, so why not give out scales? Let the government give out scales to those who want one. It will be cheap for them. It would cost them probably about $50 a scale and they could save millions if they could prevent you from getting diabetes or hypertension.

A number of my colleagues believe that the government should step in and curb food commercials, particularly ones targeting children. I mean, it sounds reasonable but I am very skeptical because the food industry is perhaps one of the most powerful lobbies in Washington.

Wofford: What’s next for you? Are there any new weight-related research projects you’re working on?

Levitsky: My dream experiment that I’ve been trying to do for a while is to work with obese children. We know that if you don’t do anything to help a pre-adolescent obese child, they will become an obese adolescent. We also know that if you do nothing once you’ve become an obese adolescent, you are going to maintain that obesity throughout your life. The chances aren’t just extremely high, it is almost a certainty.

So what I want to do is take these pre-obese children and give them and their family scales and see if we can we get these children to grow at a slightly reduced rate by watching their weight. Could that get them into their adolescence in a non-obese state? That’s where I would like to go but I’m still trying to get funds.

Wofford: That’s a noble cause. Isn’t the obesity rate among children something shocking – like over 20 percent?

Levitsky: It is and what is more shocking is the rate at which it’s increasing. The actual rate of child obesity is lower than adult obesity but the rate at which they’re getting fatter is what’s really threatening. And that’s what I want to prevent.

Wofford: We all wish you the best of luck with that. I want to thank the audience for coming today. And thank you David, this has been illuminating for me. I’ve learned a lot today in the short time that we’ve been together.

Levitsky: My pleasure. Thank you.

Want to hear more? This interview is based on David Levitsky’s live eCornell WebSeries event, The Only Weigh to Prevent Age-Related Weight Gain. Subscribe now to gain access to a recording of this event and other Expanding Nutrition Frontiers topics.