We all know someone who can eat whatever they want but never seem to gain weight. We also have that friend who just needs to look at food to gain weight. Why does this happen? What makes one person constantly struggle with their weight while the other appears to stay thin effortlessly?

Simply put, your weight will depend on the calories you consume, the calories you store, and how many calories you burn. However, these factors are influenced by things like your genetics and environment. Both factors, as well as the types of foods you choose to consume, affect how fast you burn calories.

About Those Calories…

The calories you store and burn will depend on your genetic makeup, your level of physical activity, and your resting energy expenditure, which is defined as the number of calories your body burns while at rest. If you consistently burn all of the calories that you consume in the course of a day, you will maintain your weight. If you consume more calories than you expend, you will gain weight. Not exactly brain surgery, is it?

Excess calories are stored throughout your body as fat. Your body stores this fat in a place called adipose tissue, which is connective tissue that cushions and insulates the body. If you decrease your food intake and consume fewer calories than you burn, or exercise and burn more calories than you consume, your body will reduce some of your fat stores. When this occurs, fat cells – and your waistline – shrink.

Genetic influences

Research tells us that there are many genes that deal with our weight, but only a few of them are major players. Genes contribute to obesity by affecting appetite, metabolism, cravings, body-fat distribution, and the affinity towards eating as a way to cope with stress.

The strength of genetic influence on weight disorders varies from person to person. Research implies that the predisposition to be overweight can be anywhere from 25 to 80 percent. Some of the following characteristics might tell you how significant your genes are in contributing to your weight gain:

• You have been overweight most of your life.
• One or both of your parents or several other blood relatives are significantly overweight. If both of your parents have obesity, your likelihood of becoming obese is as high as 80 percent.
• You can’t lose weight even when you increase your physical activity and stick to a lower calorie, whole foods based diet.

Genes are most likely a lower contributor for you if you have most or all of the following characteristics:

• You eat more because food is available.
• You are moderately overweight, but you can lose weight when you follow a reasonable nutrition and exercise regimen.
• Your weight fluctuates during the holiday season, after changing your eating or exercise habits, or at times when you experience emotional stress.

These circumstances suggest that you have a genetic predisposition to be heavy, but it’s not so great that you can’t overcome it with some effort.

Our Big Fat Environment

Genetic factors are forces inside you that cause you to gain weight and stay overweight; environmental factors are the outside forces that contribute to weight gain. They include anything in our environment that makes us more likely to eat too much or exercise too little. For most of us, between car-based commuting and watching television, we sit way too much. On top of that, we’re then influenced by ads and commercials telling us to eat whatever the latest high-fat junk food is out on the market. In my opinion, this and the lack of nutrition knowledge are the driving forces for worldwide obesity.

Environmental influences come into play very early, even before you’re born. In utero exposure to smoking and/or diabetes puts an unborn baby at risk for issues with their weight. After birth, babies who are breast-fed for more than three months are less likely to have obesity as adolescents compared with infants who are breast-fed for less than three months.

Childhood habits, like drinking sugary sodas and eating high-calorie and processed foods, often cross over into adult eating habits, which promotes weight gain. Similarly, children who watch television, which is riddled with commercials for fast food and unhealthy snacks, and play video games instead of being active may be programming themselves for a sedentary future.

Portion sizes of restaurant food nowadays aren’t helping matters either. A supersized or even regular sized meal at some chain restaurants can add over 1500 extra calories to your daily allotment, which is almost a certain weight gain guarantee.

Good Ole Exercise

Ideally, we all should participate in moderate to vigorous exercise at least an hour daily. However, fewer than 25 percent of Americans meet that goal. Our daily lives don’t offer many opportunities for activity as it did when we were children, but even children don’t exercise as much in school often because of cutbacks in physical education classes.

People drive to work, sit at a desk all day, sit in the car to drive home, sit on the couch to watch television and eat more food, and then get into bed. Less of us are walking to local shops. We drive to one-stop megastores, park close to the entrance, wheel our purchases in a shopping cart, and drive home. The widespread use of easy-to-use cleaning appliances also takes nearly all the physical effort out of daily chores.

Stress, Sleep, Etc.

While there are a number of different aspects of American society that may conspire to promote weight gain, stress is the most common. People work long hours and take shorter or less frequent vacations. When both parents in a family work, it’s harder to find time to shop, prepare, and eat healthy foods together. Between driving kids to playdates and activities and worrying about their health and safety, parents have a lot to stress about on top of other commitments. Deadlines, events, and other time-related pressures often lead people to eat on the run and sacrifice sleep, both of which can contribute to weight gain.

Research claims that the very act of eating irregularly and on-the-go may contribute to obesity, too. Irregular eating patterns may disrupt the effectiveness of our inner eating cues in a way that promotes corpulence.

Many studies also suggest that the less you sleep, the more likely you are to gain weight. Lack of sufficient sleep disturbs the hormones, leptin, and ghrelin, which control hunger and appetite. Researchers found that people who slept less than eight hours a night had higher levels of body fat than those who slept more, and the people who slept the fewest hours weighed the most.

Stress and lack of sleep are closely connected to psychological well-being, which can also affect diet and appetite, as anyone who’s ever gorged on cookies or potato chips when feeling anxious or sad can attest. Some people eat more when affected by depression, anxiety, or other emotional disorders. In turn, being overweight and obese on its own can promote emotional disorders.

If you repeatedly try to lose weight and fail, or if you succeed in losing weight only to gain it all back, the struggle can cause tremendous frustration over time. Unfortunately, this can cause or worsen anxiety and depression. A negative cycle develops that leads to even greater obesity, associated with increasingly severe emotional and physical difficulties.

What Can We Do to Stop This?

The answers seem simple enough, but the motivation has to come along with that. See a professional, get together with a group of friends to plan a fun physical activity, and learn about healthy eating if you feel you don’t really know where to start. Turn off the television and read a book. Leave your cell phone off or in another room at night so you can try to get better sleep. Park far away when you shop.

Small steps can go a long way. Deal with the fact that your body does change as you age, and you should try to love and accept it, while treating it the best way you know how.