Why people become overweight

Everyone knows some people who can eat ice cream, cake, and whatever else they want and still not gain weight. At the other extreme are people who seem to gain weight no matter how little they eat. Why? What are the causes of obesity? What allows one person to remain thin without effort but demands that another struggle to avoid gaining weight or regaining the pounds he or she has lost previously?

On a very simple level, your weight depends on the number of calories you consume, how many of those calories you store, and how many you burn up. But each of these factors is influenced by a combination of genes and environment. Both can affect your physiology (such as how fast you burn calories) as well as your behavior (the types of foods you choose to eat, for instance). The interplay between all these factors begins at the moment of your conception and continues throughout your life.

The calorie equation

The balance of calories stored and burned depends on your genetic makeup, your level of physical activity, and your resting energy expenditure (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 energy (calories) than you expend, you will gain weight.

Excess calories are stored throughout your body as fat. Your body stores this fat within specialized fat cells (adipose tissue) — either by enlarging fat cells, which are always present in the body, or by creating more of them. If you decrease your food intake and consume fewer calories than you burn up, or if you exercise more and burn up more calories, your body will reduce some of your fat stores. When this happens, fat cells shrink, along with your waistline.

Genetic influences

To date, more than 400 different genes have been implicated in the causes of overweight or obesity, although only a handful appear to be major players. Genes contribute to the causes of obesity in many ways, by affecting appetite, satiety (the sense of fullness), metabolism, food cravings, body-fat distribution, and the tendency to use eating as a way to cope with stress. The strength of the genetic influence on weight disorders varies quite a bit from person to person. Research suggests that for some people, genes account for just 25% of the predisposition to be overweight, while for others the genetic influence is as high as 70% to 80%. Having a rough idea of how large a role genes play in your weight may be helpful in terms of treating your weight problems.

How much of your weight depends on your genes?

Genes are probably a significant contributor to your obesity if you have most or all of the following characteristics:

• You have been overweight for much 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 developing obesity is as high as 80%.

• You can't lose weight even when you increase your physical activity and stick to a low-calorie diet for many months.

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

• You are strongly influenced by the availability of food.

• You are moderately overweight, but you can lose weight when you follow a reasonable diet and exercise program.

• You regain lost weight during the holiday season, after changing your eating or exercise habits, or at times when you experience psychological or social problems.

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.

At the other end of the spectrum, you can assume that your genetic predisposition to obesity is modest if your weight is normal and doesn't increase even when you regularly indulge in high-calorie foods and rarely exercise.

People with only a moderate genetic predisposition to be overweight have a good chance of losing weight on their own by eating fewer calories and getting more vigorous exercise more often. These people are more likely to be able to maintain this lower weight.

What are thrifty genes?

When the prey escaped or the crops failed, how did our ancestors survive? Those who could store body fat to live off during the lean times lived, and those who couldn't, perished. This evolutionary adaptation explains why most modern humans — about 85% of us — carry so-called thrifty genes, which help us conserve energy and store fat. Today, of course, these thrifty genes are a curse rather than a blessing. Not only is food readily available to us nearly around the clock, we don't even have to hunt or harvest it!

In contrast, people with a strong genetic predisposition to obesity may not be able to lose weight with the usual forms of diet and exercise therapy. Even if they lose weight, they are less likely to maintain the weight loss. For people with a very strong genetic predisposition, sheer willpower is ineffective in counteracting their tendency to be overweight. Typically, these people can maintain weight loss only under a doctor's guidance. They are also the most likely to require weight-loss drugs or surgery.

The prevalence of obesity among adults in the United States has been rising since the 1970s. Genes alone cannot possibly explain such a rapid rise. Although the genetic predisposition to be overweight varies widely from person to person, the rise in body mass index appears to be nearly universal, cutting across all demographic groups. These findings underscore the importance of changes in our environment that contribute to the epidemic of overweight and obesity.

Environmental causes of obesity

Genetic factors are the forces inside you that help you gain weight and stay overweight; environmental factors are the outside forces that contribute to these problems. They encompass anything in our environment that makes us more likely to eat too much or exercise too little. Taken together, experts think that environmental factors are the driving force for the causes of obesity and its dramatic rise.

Environmental influences come into play very early, even before you're born. Researchers sometimes call these in-utero exposures "fetal programming." Babies of mothers who smoked during pregnancy are more likely to become overweight than those whose mothers didn't smoke. The same is true for babies born to mothers who had diabetes. Researchers believe these conditions may somehow alter the growing baby's metabolism in ways that show up later in life.

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 often stick with people for the rest of their lives. Kids who drink sugary sodas and eat high-calorie, processed foods develop a taste for these products and continue eating them as adults, which tends to promote weight gain. Likewise, kids who watch television and play video games instead of being active may be programming themselves for a sedentary future.

Many features of modern life promote weight gain. In short, today's "obesogenic" environment encourages us to eat more and exercise less. And there's growing evidence that broader aspects of the way we live — such as how much we sleep, our stress levels, and other psychological factors — can affect weight as well.

The food factor as one of the causes of obesity

According to the Centers for Disease Control and Prevention (CDC), Americans are eating more calories on average than they did in the 1970s. Between 1971 and 2000, the average man added 168 calories to his daily fare, while the average woman added 335 calories a day. What's driving this trend? Experts say it's a combination of increased availability, bigger portions, and more high-calorie foods.

Practically everywhere we go — shopping centers, sports stadiums, movie theaters — food is readily available. You can buy snacks or meals at roadside rest stops, 24-hour convenience stores, even gyms and health clubs. Americans are spending far more on foods eaten out of the home: In 1970, we spent 27% of our food budget on away-from-home food; by 2006, that percentage had risen to 46%.

In the 1950s, fast-food restaurants offered one portion size. Today, portion sizes have ballooned, a trend that has spilled over into many other foods, from cookies and popcorn to sandwiches and steaks. A typical serving of French fries from McDonald's contains three times more calories than when the franchise began. A single "super-sized" meal may contain 1,500–2,000 calories — all the calories that most people need for an entire day. And research shows that people will often eat what's in front of them, even if they're already full. Not surprisingly, we're also eating more high-calorie foods (especially salty snacks, soft drinks, and pizza), which are much more readily available than lower-calorie choices like salads and whole fruits. Fat isn't necessarily the problem; in fact, research shows that the fat content of our diet has actually gone down since the early 1980s. But many low-fat foods are very high in calories because they contain large amounts of sugar to improve their taste and palatability. In fact, many low-fat foods are actually higher in calories than foods that are not low fat.

The exercise equation

The government's current recommendations for exercise call for an hour of moderate to vigorous exercise a day. But fewer than 25% of Americans meet that goal.

Our daily lives don't offer many opportunities for activity. Children don't exercise as much in school, often because of cutbacks in physical education classes. Many people drive to work and spend much of the day sitting at a computer terminal. Because we work long hours, we have trouble finding the time to go to the gym, play a sport, or exercise in other ways.

Instead of walking to local shops and toting shopping bags, we drive to one-stop megastores, where we park close to the entrance, wheel our purchases in a shopping cart, and drive home. The widespread use of vacuum cleaners, dishwashers, leaf blowers, and a host of other appliances takes nearly all the physical effort out of daily chores and can contribute as one of the causes of obesity.

The trouble with TV: Sedentary snacking

The average American watches about four hours of television per day, a habit that's been linked to overweight or obesity in a number of studies. Data from the National Health and Nutrition Examination Survey, a long-term study monitoring the health of American adults, revealed that people with overweight and obesity spend more time watching television and playing video games than people of normal weight. Watching television more than two hours a day also raises the risk of overweight in children, even in those as young as three years old.

Part of the problem may be that people are watching television instead of exercising or doing other activities that burn more calories (watching TV burns only slightly more calories than sleeping, and less than other sedentary pursuits such as sewing or reading). But food advertisements also may play a significant role. The average hour-long TV show features about 11 food and beverage commercials, which encourage people to eat. And studies show that eating food in front of the TV stimulates people to eat more calories, and particularly more calories from fat. In fact, a study that limited the amount of TV kids watched demonstrated that this practice helped them lose weight — but not because they became more active when they weren't watching TV. The difference was that the children ate more snacks when they were watching television than when doing other activities, even sedentary ones.

Stress and related issues

Obesity experts now believe that a number of different aspects of American society may conspire to promote weight gain. Stress is a common thread intertwining these factors. For example, these days it's commonplace to work long hours and take shorter or less frequent vacations. In many families, both parents work, which makes it harder to find time for families to shop, prepare, and eat healthy foods together. Round-the-clock TV news means we hear more frequent reports of child abductions and random violent acts. This does more than increase stress levels; it also makes parents more reluctant to allow children to ride their bikes to the park to play. Parents end up driving kids to play dates and structured activities, which means less activity for the kids and more stress for parents. Time pressures — whether for school, work, or family obligations — often lead people to eat on the run and to sacrifice sleep, both of which can contribute to weight gain.

Some researchers also think that the very act of eating irregularly and on the run may be another one of the causes of obesity. Neurological evidence indicates that the brain's biological clock — the pacemaker that controls numerous other daily rhythms in our bodies — may also help to regulate hunger and satiety signals. Ideally, these signals should keep our weight steady. They should prompt us to eat when our body fat falls below a certain level or when we need more body fat (during pregnancy, for example), and they should tell us when we feel satiated and should stop eating. Close connections between the brain's pacemaker and the appetite control center in the hypothalamus suggest that hunger and satiety are affected by temporal cues. Irregular eating patterns may disrupt the effectiveness of these cues in a way that promotes obesity.

Similarly, research shows that the less you sleep, the more likely you are to gain weight. Lack of sufficient sleep tends to disrupt hormones that control hunger and appetite and could be another one of the causes of obesity. In a 2004 study of more than 1,000 volunteers, 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. Studies have demonstrated that some people eat more when affected by depression, anxiety, or other emotional disorders. In turn, overweight and obesity themselves 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, which can cause or worsen anxiety and depression. A cycle develops that leads to greater and greater obesity, associated with increasingly severe emotional difficulties.

This blog was written by Harvard Health

9 simple health goals that you can keep

Try these small changes to improve your health in 2021

1. Walk more

Brisk walking, even for just 10 minutes a day, can improve your circulation, boost your mood and improve your sleep. If you want to start walking more in 2021, try doing it in 10 minute chunks to make it less daunting. 

Remember, you can tell if you're walking briskly enough if you're able to talk, but you're breathing faster than usual.

2. Experience nature

Mental health charity Mind found that proximity to nature can have positive wellbeing benefits, including helping you feel more relaxed and less angry.

If your able visiting green spaces more often can be really beneficial. One study found, for example, that just hearing birdsong can boost mental well-being for four hours or more.

You can bring nature into your everyday life by having flowers in the house, looking after house plants, growing your own food or exercising outdoors.

3. Spend less time sitting down

Sitting is the new smoking – the body wasn't built for spending hours at a desk or in front of the TV. It increases your risks of cardiovascular disease, diabetes and breast, colon and colorectal cancer. Why not try the Pomodoro method to break up desk time.

Set a timer to break each hour into two 25-minute blocks separated by two five-minute breaks. Work intently during the work periods and move about during the breaks. Use your breaks to stand up, do a quarter squat, do some rotations, or just go for a walk round the office. This technique can also boost your focus when you're working.

4. Get good sleep

Being sleep deprived can negatively affect your mental and physical health. It can even make you prone to major illnesses, from obesity to depression. Reducing screen time before bed, sleeping in a cool room, and going to bed at the same time each evening all help with a good night's rest. Apps such as Sleep Cycle can help you pinpoint any issues and help you to improve your sleep. For more tips, see our article on how to improve your sleep.

5. Stretch

Many of us want to become more flexible and introducing stretches into your daily routine can help you achieve that. Dynamic stretching can help improve flexibility and range of movement, and decrease the risk of injury.

Make a habit of stretching when you wake up, or while you're waiting for the kettle to boil. Discover more ways to boost your flexibility, including stretches to try.

6. Make food more fun

Challenge your self to cook and eat something one new recipe every week. As well as vitamins and minerals, there are hundreds of micronutrients known as phytochemicals in food. Eating a wide variety of food is an easy way of ensuring we get a good nutritional mix. If you're looking to shake things up, why not try one of our delicious, healthy recipes, with ideas for breakfast, lunch and dinner.

7. Plan meals

A focused food shopping list cuts calories and waste, and saves money, as you only buy what you need (and throw nothing away). Take the time to plan your meals, and write out a list before you go to the shops.

8. Reach out to others

We're all busy, but in 2021 take time out for your relationships. The Mental Health Foundation says that having good quality relationships can help us to live longer and happier lives with fewer mental health problems. 

Try to schedule calls (or in-person meetings) with your friends on a regular basis rather than leaving it up to chance. You can increase your sense of belonging by joining clubs or volunteering in your area. If you can't get out and about, there are plenty of online communities you can join - from book clubs to parent/grandparent groups. For your romantic relationships, reflect on whether you're in a healthy relationship.

9. Drink plenty of water 

Drinking enough water is crucial to good health. The NHS recommends drinking 6-8 glasses of water a day (or 1.5 to 2 litres in total). This includes lower fat milks, and low sugar or sugar-free drinks, tea and coffee within this intake. 

You can meet this target by buying a reusable water bottle and keeping it with you throughout the day. If you know your bottle holds 500ml, you know you have to refill it 3 to 4 times to drink the recommended amount. Don't forget that you need more water if you exercise, or on hot days.

Men’s Belly Fat

If you're carrying a few extra pounds, you're not alone. But this is one case where following the crowd isn't a good idea. Carrying extra weight — especially belly fat — can be risky.

Michael D. Jensen, M.D., an endocrinology specialist at Mayo Clinic, Rochester, Minn., answers common questions about belly fat in men.
The trouble with belly fat is that it's not limited to the extra layer of padding located just below the skin (subcutaneous fat). It also includes visceral fat — which lies deep inside your abdomen, surrounding your internal organs.
Regardless of your overall weight, having a large amount of belly fat increases your risk of:

• Cardiovascular disease

• Type 2 diabetes

• Colorectal cancer

• Sleep apnea

Your weight is largely determined by how you balance the calories you eat with the energy you burn. If you eat too much and exercise too little, you're likely to pack on excess pounds — including belly fat.

However, aging plays a role. As you age, you lose muscle — especially if you're not physically active. Loss of muscle mass decreases the rate at which your body uses calories, which can make it more challenging to maintain a healthy weight. In addition, in some men fat cells in the arms and legs lose the ability to store fat, which causes any excess fat to go to the abdomen.

Your genes also can affect your chances of being overweight or obese, as well as play a role in where you store fat.
Drinking excess alcohol can cause you to gain belly fat — the "beer belly." However, beer alone isn't to blame. Drinking too much alcohol of any kind can increase belly fat, although some research suggests wine might be an exception.

If you drink alcohol, do so only in moderation. The less you drink, the fewer calories you'll consume and the less likely you'll be to gain belly fat.
So how do you know if you have too much belly fat? Simply measure your waist:

• Stand and place a tape measure around your bare stomach, just above your hipbone. If your belly droops, lie down to take the measurement.

• Pull the tape measure until it fits snugly around you, but doesn't push into your skin.

• Make sure the tape measure is level all the way around.

• Relax, exhale and measure your waist, resisting the urge to suck in your stomach.

For men, a waist measurement of more than 40 inches (102 centimetres) indicates an unhealthy concentration of belly fat and a greater risk of health problems.

You can tone abdominal muscles with crunches or other targeted abdominal exercises, but just doing these exercises won't get rid of belly fat. However, visceral fat does respond to the same diet and exercise strategies that can help you shed excess pounds and lower your total body fat.

To battle the bulge:

• Eat a healthy diet. Emphasize plant-based foods, such as fruits, vegetables and whole grains, and choose lean sources of protein and low-fat dairy products. Limit saturated fat, found in meat and high-fat dairy products, such as cheese and butter. Choose moderate amounts of monounsaturated and polyunsaturated fats — found in fish, nuts and certain vegetable oils — instead.

• Keep portion sizes in check. Even when you're making healthy choices, calories add up. At home, slim down your portion sizes. In restaurants, share meals — or eat half your meal and take the rest home for another day.

• Include physical activity in your daily routine. For most healthy adults, the Department of Health and Human Services recommends moderate aerobic activity, such as brisk walking, for at least 150 minutes a week or vigorous aerobic activity, such as jogging, for at least 75 minutes a week. In addition, strength training exercises are recommended at least twice a week. If you want to lose weight or meet specific fitness goals, you might need to exercise more.

To lose excess fat and keep it from coming back, aim for slow and steady weight loss — up to 2 pounds (1 kilogram) a week. Consult your doctor for help getting started and staying on track.
Remember, you can lose belly fat — it just takes effort and patience. In fact, shedding even a few extra pounds can help you feel better and lower your risk of health problems.