Weight loss: more than just eating less and being more active

Dr Paula Diab sheds light on the physiological mechanism of weight loss and gain then looks at the methodologies that can assist in achieving and maintaining the desired weight.

Did you make any New Year’s resolutions for planned weight loss, go on diet, spend more time in the gym or start some new type of exercise? Have you kept up with any of those goals as yet?

Don’t feel alone or despondent about these goals. In this fast-paced, instant-gratification world in which we live, such goals are extremely common. However, the rewards aren’t as easy to achieve as we think they are.

Obesity as a chronic disease

Obesity has recently been recognised by the international healthcare community as a chronic disease. What this means is that the mechanisms that cause obesity are persistent and long-lasting and various complications may be associated with the condition as well.

The European Medicines Agency states that “Obesity is recognised as a chronic clinical condition that usually requires long-term therapy to induce and maintain weight loss and is considered to be the result of complex interaction of genetic, metabolic, environmental and behavioural factors, which are associated with increases in both morbidity and mortality.”

The World Health Organization has recognised obesity as a threat to both developed and developing countries and estimates that over 650 million people worldwide are affected by it.

The Canadian Medical Association has declared “obesity to be a chronic medical disease requiring enhanced research, treatment and prevention efforts.”

The bottom line is that treating obesity is more complicated than cutting out sweets and going to gym more often.

What is obesity?

Many people and healthcare institutions consider a body mass index (BMI), a simple height to weight ratio, as the only indicator of being over or underweight. In addition, it’s suggested that all types of people from all races and ethnic backgrounds be subject to the same parameters. Some exceptions have been made but generally a BMI of > 25 is considered overweight and > 30 is obese.

This is also changing. I’m not a big follower of action movies but my teenage son tells me that Dwayne Johnson (aka The Rock) is 1.96m tall and weighs 118kg. That gives him a BMI of 34; very soundly in the obese category. I’ll certainly be last in the queue of people to go up to him and tell him he’s overweight.

More recently, we have started looking at a multitude of other factors to determine if someone is overweight and how this may or may not affect their health. Some of the factors we consider are:

  • Medical co-morbidities – cardiac disease, arthritis, fertility problems, diabetes, etc
  • Mental concerns – depression, social isolation, etc.
  • Functional ability – can the person continue their desired daily activities without limitation?

These are all important indicators that will guide as to how we should approach the management of obesity. Few would argue that The Rock has any limitations on his functional abilities.

Complications of obesity

Does this mean that we can ignore a higher BMI and allow people to choose their desired weight as they please? Not really. Research indicates that people with a higher BMI are definitely prone to developing a range of complications and that obesity has a significant impact on life expectancy. People with a BMI over 40 have a predicted only 50% chance of reaching the age of 70 compared to those with a BMI < 30 who have an 80% chance.

Complications range from other metabolic diseases, such as diabetes, which has a significant impact on other health concerns in itself, to cardiovascular disease and some types of cancers.

Gout, arthritis and bone disease also become more prevalent due to the mechanical strain on joints and muscles and mental health complications, such as depression, also are more frequent.

Weight loss improves complications

Whilst this may sound like a very negative situation, the reality is even a modest weight loss will have an enormous effect on reducing these complications.  

What causes obesity?

It’s probably fair to say that most people think that weight gain is due to an imbalance between energy intake and energy expenditure. People who are overweight, either eat too many calories or do too little activity. Losing weight therefore requires more activity or fewer calories. This is not true.

It has now been scientifically proven that weight gain or loss is far more complex than this and that the main organ responsible for controlling weight is our brain.Genetics play a vital role in regulating this control; if your family is overweight, it’s very likely that you have similar genes that will dictate how your body responds. Other organs in the body such as the pancreas, gut and adipose tissue (fat tissue) also influence your metabolism and how you process energy in the body.

Restricting energy intake (eating less) is also not an effective means of weight loss as hormones, such as leptin, are downregulated as energy restriction occurs. Low leptin levels cause the body to conserve energy and trigger a response in the brain that you are hungry and need to eat. This is not a will-power issue but a genuine lack of energy in the body which causes weight to regain as your body adapts to the feeling of hunger and desire to eat.

The role of the brain in controlling appetite

Until recently, the impact of the brain in appetite has been largely overlooked. Homeostatic eating is eating for hunger. This is what we generally don’t do. It is, however, what most animals do. They hunt when they are hungry and eat until they have gained enough calories to survive.

Hedonic eating

Hedonic eating is eating for pleasure and is under control of the mesolimbic system. This is the eating that happens at Christmas lunch or at a wedding or when we eat out at a restaurant with friends. It’s mediated by feelings of wanting or liking to eat and not by satiety or hunger.

A want-to-eat is mediated by dopamine, a hormone implicated in reward-behaviour system. The more we eat, the more we reward our brain and drive future such behaviours. Liking-to-eat is associated with pleasure derived from eating and is mediated through opioid and cannabinoid receptors. No one would dream of hosting a celebration and serving just a small amount of food to allow your guests to survive and combat starvation. We like tasting different foods, we like socialising while we eat, we like food that tastes good.

We have the privilege of being able to indulge in hedonic eating and not just eat when we are hungry. It’s the executive functioning in the pre-frontal cortex of our brains that decides when we are hungry. Over years of over-riding the need to eat and the want to eat, our brains develop alternate pathways.

In addition, each time we gain weight, our brains use that as a new set-point, a new normal to which it governs our weight regain. Many of us will relate to the experience of going on a diet, eating fewer calories but as soon as you go into a maintenance phase again, you regain the weight to where you were initially.

How do medications work?

Some older weight loss preparations have a more short-term effect and aim to speed up metabolism; these generally work very well in the short-term but have little effect on the underlying problem.

Others act on energy wastage and bind fat in the gut to reduce calories absorbed. Again, this can work well in the short-term but aside from some negative side effects, do very little to address the pathways in the brain.

Newer formulations of medications to manage weight have recently been developed and licenced for use and are much more effective at addressing the chronic underlying pathology that results in weight gain.

What we need is a drug that acts on the pathways in the brain to reset the weight set-point and override the feelings of hunger and desire to eat as well as improve metabolism in the gut, pancreas and other metabolic organs.

By reducing gastric emptying, you feel fuller for a longer period of time thus decreasing the desire to eat. Within the liver, metabolism is also affected reducing glucose production and enhancing glucose sensitivity.

Such drugs also have a positive effect on cardiac function, but the most significant effect is the action directly on the brain which results in decreased food intake, improved satiety and sustained weight loss.

Patient feedback

There has been great success using these drugs with my patients and some of the comments talk directly to the mechanisms in which they work. Comments relating to how their focus shifts away from food and they can get on with normal daily activities without being fixated about their next meal or how little they should be eating.

Other comments relating to the ability to sit at a table and eat what they feel they need to eat rather than what they want to eat and actually feel full and satisfied at the same time. The medication also has a significant effect on combatting the cravings that people feel in between meals and the extra snacks that we have just because they taste nice.


Shifting from a BMI-centric approach of treatment where we are purely trying to target a number to a more complication-centric focus where the multiple co-morbidities associated with obesity are addresses as well as the often unseen mental complications will certainly result in better outcomes in managing weight and obesity.

Counselling, self-monitoring, physical activity and diet are most certainly vital aspects of weight management achieved through interaction with a holistic multi-disciplinary team. This includes dietitians to address the obvious aspects of diet and a doctor skilled in obesity management to know which drugs and possible surgical options suit each patient as well as multiple other practitioners as individual patient needs dictate.

Our healthcare system is perhaps not ideally suited to deliver obesity management in such a way, but it will be a great leap forward if we can shift our focus from thinking that weight loss is a quick-fix that requires more activity and fewer calories to one of understanding the chronic nature and multi-faceted cause of weight gain.

Accurate and effective pharmacological treatment is the future of weight management and treating obesity as a disease and not a lack of will power and poor decision-making will go a long way to helping those who need medication to access it.

Dr Paula Diab


Dr Paula Diab is a diabetologist at Atrium Lifestyle Centre and is an extra-ordinary lecturer, Dept of Family Medicine, University of Pretoria.

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