Causes of Obesity

Is it biology or Psychology?

Obesity is a biological problem. It is becoming increasingly clear that obesity is largely due to a very powerful built in weight control system that is very stubborn. We all understand how weight gain occurs: eating too much for what your body needs. How people get this out of balance is pretty easy to understand. It is because it is really difficult to know from looking at your food and your lifestyle what exactly is the required amount of food. And also, we aren't always focused on getting this exactly right every day, or in fact know how to. ISo once the calories are out of balance and the weight goes up a little we need to redress this straight away before the weight goes up too far or for too long. Otherwise the part of the brain that controls your weight will believe this new weight is the required weight and will reset itself to maintain this new weight. So, the main cause of obesity is excessive calories coupled with not noticing the weight gain and the body resetting to an elevated weight. So, when you have noticed your weight gain and the excess calories and try to redress this, you have to outsmart and overcome a very complex, stubborn and effective system determined to keep your weight exactly where it is. The more dieting that is attempted, the more this system is stimulated to resist weight loss. And then, on top of this is the emotional response to the new weight, and to the attempts to lose weight etc.

So, for whatever the reason some people get their calorie balance out of whack, whether psychological, lifestyle related, eating style etc, once there is a sustained weight problem, it is likely to persist.



Your genes determine how your body works. Your genes determine how you are different to everybody else , but also how it is so similar to everybody else. There is nothing you can do about changing your genes, of course. Surprisingly there are almost no identified genetic abnormalities that cause obesity. If there were, this might help develop clever and individualised treatments. There are clearly some families that have a tendency to obesity, and some of these may have a genetic cause. However, for most obese families there is no clear genetic cause.

What Can You Do About Obesity?


How your body turns food into energy. If you eat the same amount of food as another person, you might gain weight and they don’t. They have a higher metabolic rate (assuming they don’t exert themselves more). Either way, the calorie-in to calorie-out balance needs to be just right for the body’s metabolism. What is too much food for one person is the right amount for another.

There are many causes of obesity. We have no control over most of them.

Eating Habits

We need to eat a certain way to maintain a healthy weight. But what is the perfect way? Nobody really knows, but there are some eating patterns which are clearly not good for weight control. So your eating habits may be contributing to your weight problem. There are a number of eating styles, which are not compatible with good weight control. Some of these are:

  • Fasting and feasting: poor (low) calorie intake for most of the day followed by hunger ( and sometimes excessive or even unbearable hunger ) and then catch up eating, that never seems to satisfy. Some people, knowing that calories increase your weight try skipping meals. Then they start eating later in the day and then don’t seem to be able to stop eating. They are “fasting and feasting”. This eating style is terrible for weight control.
  • Quick eaters: The speed of eating is closely tied to weight control. People who eat their food quickly are more likely to be obese. This makes sense when you think of fullness. It stakes around 10 to 20 minutes to feel full, no matter what you have eaten. If in that time you have eaten a large meal and gone back for seconds or thirds and then had desert, you will have eaten much more than the person who is still tucking into their first course. Also, you are less likely to remember what or how much you have eaten if it goes down very quickly. If food tastes really nice, and we want more, we are likely to eat less and therefore less calories if we savour every mouthful and eat slowly. So eating slowly is like a substitute for having more.
  • Emotional Eaters: See below (Psychological Factors), but basically eating associated with various emotions. We are emotional creatures, but if emotions are connected strongly to eating this makes weight control more challenging.
  • Pleasure Eaters: “So many yummy foods, so little time, I love to eat, bring me some more. I love food!” It can be hard to limit eating when it is so pleasurable!
  • Habitual Eaters: This is eating the same food over and over again, because (so you think) you are “addicted” to it. What is really happening here is that a well-worn habit of eating a certain food is giving you an excess of that food, and of course the calories that go with it. It can be very hard to break a food habit! It also refers to people who eat for reasons that have nothing to do with hunger, such as having a cake with a cuppa, just because…
  • Non-Pragmatic Eaters: Pragmatic eaters eat only those foods that they have calculated their body needs. Eg “I need to eat more protein today, because I went to the gym and did weight training.”, “I haven’t eaten my serve of fruit today. I’ll have an apple.” These people are very unlikely to have a weight problem. We should all eat like this to a certain extent. Non-pragmatic eaters never think like this and are more likely to struggle with their weight.
  • Many, many more

Exercise Habits

Family Fitness

More active people use up more calories. But once you have a weight problem, just moving around can be exhausting and joints hurt and, essentially, exercising is quite unpleasant. So overweight people tend to use less calories. Even so, some obese people use up more calories than lean people.

Exercise is either formal (going to the gym) or informal (doing the housework, speed walking to catch the train, standing up on the train…). Obesity is associated with less informal exercise.

What Can You Do About Obesity?


People with a weight problem tend to have something about their life, which makes them more likely to gain weight. It might be shift work, a busy lifestyle with not enough time in the day for most things let alone time to prepare healthy food. Or a lifestyle that has only any quiet time at the end of the day, and then food becomes part of the wind-down ritual for the day. Some other patterns are:

  • “Weekend blow out”: Calorie controlled diet for most of the time, and then a period of excessive calories often at the weekend, such as going out to dinner and basically “letting your hair down”.
  • Social eaters. Dining out with friends, having fun, you’re not really focusing on the high level of calorie intake, because now is not the time to fuss over calories, too busy having fun…

Life Changes

As life changes, our diet needs to change to match. Middle aged men frequently report weight gain when they stopped playing footy, and women often say their weight control battle got harder after having children (also hormonal? Perhaps), and men and women often say it all started when they left home and their lifestyle changed.


Hormones play an important role in weight control. There are so many hormones involved that it is proving nigh on impossible to isolate a hormone that will help with a wonder medication unfortunately. Certainly some hormone play such important roles in weight control that if they are deranged, weight increases such as in particular thyroid hormones and Cortisol.


There are numerous families of overweight and obese people. This is mostly due to the family’s overall approach to food, weight control and exercise, as well as genes. Some counties, like Australia, have large numbers (percent per capita) with a major weight problem, whereas others like China have a small weight problem. Same thing for different parts of Australia, and Australia today versus 100 years ago. It all relates to our cultural approach to food, weight and exercise.

Food is pleasurable. It makes us feel better when we are depressed or stressed.

What Can You Do About Obesity?

Psychological Factors

Many people eat for emotional reasons. Eating helps them deal with stress, boredom, sadness, block out a distressing thought. Food is pleasurable for all of us and it helps to relieve our stress. There are nice smells, and colours and tastes and there are chemicals in food that actually make us feel different. Eg chocolate, coffee. There is nothing particularly wrong with eating for emotional reasons, unless the food is making the weight go up and causing a weight problem. But people often refer to themselves as being bad or their food being bad.

This is all part of the psychological battle to feel good about ourselves while trying to eat the things our body’s need.

Please Contact Melbourne Bariatrics on  03  9770  7189  for more information or to make an appointment
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