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Fighting Obesity: The Role of Behavior, Biology and Bad Choices
Part 1 in a four-part series on obesity and weight loss

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What Makes You Fat

Although skinny people sometimes attribute fatness to laziness, it’s not so simple. There are plenty of thin, lazy people who eat poorly and get no exercise. The reason that some people become fat is a complex interaction between who they are and how they live.

Your genes absolutely play a role. If you have one parent who is fat, your risk is increased. If both parents are fat, your risk is increased even more. Researchers estimate that as much of 60 percent of obesity risk is genetic. So far over 600 genes and chromosomal regions have been linked with human obesity, but more are being decoded all the time. Still, we do know that for most people, there are many factors involved and it’s not genes alone that determine obesity. Although you may share DNA with your parents, you may also share lifestyle behaviors that encourage you to be—and keep you—fat.

One just needs to look at what’s happening in the U.S. for proof. The human genome has not changed in the past two decades, but obesity levels have dramatically increased in this country during that time. What has changed is the way that people live: The environment is obesigenic, or, rather, it helps to make you fat. All the junky fast food, calorie-filled drinks, huge portions and couch-potato, car-driving, desk-working living have triggered those who are prone to it to become obese. In another environment where famine was a reality, these people might have lived the longest. But in this modern setting, they may end up with heart disease, diabetes and other conditions that result from carrying too much fat. If you are fat, you may not have control over whether you are susceptible to packing on extra weight, but you do have control over how much weight you gain.

What Keeps You Fat

In this obesigenic environment, everyone is prone to weight gain, even lean people. They may not become obese, but they can easily gain one or two pounds a year so that from ages 20 to 50 they may have gradually gained 30 or more pounds. The first study ever to assess the long-term risk of weight gain was done on 4,000 white adults who were part of the well-known Framingham Study. Over a 30-year period, researchers found that 90 percent of the men and 70 percent of the women became overweight and 33 percent became obese. A large majority went from being overweight to obese in just a four-year period. That quick transition suggests that lifestyle behaviors—what you eat, how you active you are—are behind the rapid rise. The good news is that you can live a leaner lifestyle. It’s not always easy, but it can be done.

It is easier to gain weight than to lose it, and it is easier to lose it than to keep it off. Fat-prone folks may have an even easier time gaining and an even harder time losing—and maintaining that loss—than lean people. Individual biological differences are the culprit. For example, hormones, neurotransmitters and other physiological factors may be secreted in different amounts or at different times than in a lean person—and this can affect all aspects of eating and activity. For example, you might have a faster release of the hormone that makes you hungry. Or you may have a higher threshold of food intake before factors that trigger satiety kick in, which means you may feel less full from the same-sized meal as someone else. Or, pictures of food in a TV commercial might spark a craving that prompts you to seek out something to eat, whereas a lean person might not have that same mental response.

How active you tend to be may also be dictated by biological factors. You may be less prone to fidgeting and more inclined to sit throughout the day. You may experience fewer sensations of pleasure and enjoyment from, say, riding a bike than a regular exerciser would. (And that can affect how easy it is for you to stick to a fitness regimen.) If you do diet and lose weight, you may trigger a biochemical surge that spikes your appetite more than normal, which means you’ll need to exert tough love on yourself to fight the urge to gorge. You might not even have to eat more for your body to be predisposed to storing more fat than another person.

These sorts of internal processes mean that, as a fat person, you may not be on level ground with an always-lean person. And you may have to work harder to keep your weight under control. But you can do it, and you can make it easier by working smarter. The first step is understanding your status, your limitations and the obstacles you may face.