6 minutes to read
Understanding hunger, the brain, and how it may lead to obesity
Did you know that around 2 in 3 adult Australians are considered overweight or obese?1 Over the past twenty years, the rates of obesity have been rising across the country1 – but does this mean we are a hungry nation? What does hunger have to do with obesity when we have so much food available? Read on to find out.
What is hunger?
Hunger is simply the name given to the sensation of requiring food.2 When you experience the feeling of hunger, it is your brain trying to motivate you to seek out food and eat it. Hunger actually occurs in three stages:2,3
- Hunger – the desire to eat
- Satiation – the sensation of fullness that signals you to stop eating
- Satiety – the period of time before you feel hungry again
The brain circuits involved in obesity
Let’s look at the pathways of decision-making that lead to food consumption. There are two systems that manage how your body maintains weight - the homeostatic system (the parts that control hunger and metabolism) and the hedonic system (the reward system) which work together in balance.4
The homeostatic system includes the hypothalamus in the brain as well as hormones from the gut and fat cells which sense energy levels and signal the brain when they drop (by making you feel hunger).4 The feeling of hunger then drives the cognitive regions to act to get and consume food.5
The hedonic system is responsible for that pleasurable feeling you get in response to an action, in this case eating. Eating for pleasure is also called hedonic eating, which refers to eating for the pleasure of the experience, rather than hunger. By stimulating brain cells in this reward centre, foods that are high energy but low in nutrients become even more desirable, potentially leading to overeating.4
In modern times the types of food available are very triggering for the hedonic system - think of highly processed foods and foods with high energy content (but low nutritional value)6, which can trip up the balance between the homeostatic and hedonic circuits in the brain, contributing to more energy coming in than being used, which may lead to obesity.3,7
That said, the causes of obesity are far more complex and range from genetic, behavioural to environmental and psychological factors.8
It’s time to put food in its place.
Taking the first step doesn’t have to be difficult. Get started on your way to weight loss by:
Connect to a doctor online
Start an online consultation to receive weight management advice and a program that fits your needs.
Find a doctor near you
Complete a short questionnaire and get a personalised conversation guide for your doctor’s appointment. Next, easily locate a nearby GP for an in-person consultation.
Prepare for your next doctor visit
Already have a doctor you go to regularly? Fill out a short questionnaire and get a personalised conversation guide for your next doctor appointment.
4 observable obesity traits
There are four distinct observable types of obesity traits that have been identified in research. These groups, known as phenotypes, provide insights into the categorisation of obesity. Among these phenotypes, two are characterized by their association with hunger: the hungry brain and the hungry gut. The other two phenotypes are related to factors contributing to obesity that are not directly linked to hunger: emotional hunger and a reduced metabolic rate resulting in a slow burn. We will explore these phenotypes further below. 9,10
The ‘hungry brain’ type of obesity
Hungry brain is used to describe when an excessive number of calories are needed to reach that feeling of fullness (abnormal satiation).9,10 Something has gone askew in the bodily processes that tell the brain you are full and should stop eating. Feeling ‘full’ comes from volume-dependent signals from your gut – basically your stomach expands, which sends signals to your brain that you should stop eating food.2 At the same time, a hormone called cholecystokinin is produced by the cells lining your gastrointestinal tract that also signals it is time to stop eating.2
The ‘hungry gut’ type of obesity
Hungry gut describes a situation when the feeling of fullness after eating does not last as long as it should and the gut empties quickly (abnormal satiety).9,10 The feeling of satiety lasts while you are digesting your food, fading away as nutrients are absorbed.2 After you have eaten, the rate at which food moves from your stomach to your small intestines depends on the amount of food, levels of water and caloric density of the stomach contents. All these factors are assessed by various hormones and nerve signals, sending information to the rest of the gastrointestinal tract to help determine how fast to move the stomach contents through your system.2 Once the stomach contents move into the small intestine, the nutrient levels trigger feedback responses to keep things moving. Hormones are key players here, carrying signals about what you have eaten and how it is being processed to the brain. When the brain is told that there is an energy surplus, it acts to reduce food intake.2
The emotional hunger type of obesity
As described above, hormones from the gut send signals the brain to regulate hunger – but there is another system in the brain that also drives our eating behaviour and is related to emotions and pleasure around food rather than just our physiological need for food.2,9 Known as the hedonic system, this reward system in the brain becomes activated by both thoughts of eating food as well as the act of eating food, causing the release of a ‘feel good’ chemical called dopamine that reinforces the eating behaviour and food choices.3,7
Emotional hunger (or emotional eating) describes a situation of eating when in a low, or even a high mood, or when feeling anxious as a way to trigger that dopamine release and feel better. Read more here)
The slow burn type of obesity
This is where the energy that is used when resting and when physically active is low. It could also be associated with low muscle mass, all of which may contribute to a decreased metabolic rate.9,10
When hunger and reward get out of sync…
The brain is a complex beast, and pathways in the reward system and those that control hunger are interconnected.7 So, when you eat ‘rewarding’ foods that trigger the release of dopamine, your brain drives you to seek more of these types of foods – even going as far as to override the normal signals that drive hunger and satiation.3,11 The imbalance in these brain pathways that control hunger and eating behaviour can be experienced as food cravings.3,11
How do you incorporate your obesity type into a weight management plan?
Understanding how hunger and cravings both contribute to obesity may help to reinforce that everyone’s struggle with weight is different – and that a ‘one size fits all’ approach to weight management and obesity does not exist. Studies are now showing that management that tailors interventions, including diet and lifestyle, based on individual obesity phenotype may be more successful for achieving weight loss and other health benefits than a simple ‘eat less, move more’ approach. 9,10
Once you have a bit more understanding about your eating habits, take the next step to discuss what you’ve learnt with a healthcare professional. It’s important to seek help from a doctor to better understand what’s behind your overweight or obesity – and to develop a personalised approach to weight management that is tailored just for you. For advice on working with your doctor to tackle obesity, click here.
Find a doctor
To initiate an online consultation with a doctor, you can easily get started by clicking here. If you prefer to talk to a doctor face-to-face, complete this simple questionnaire and Break The Crave will send you a PDF of your answers that you can download or print, then you can find a GP with an interest in obesity management near you.
References
- Australian Government Institute of Health and Welfare, Overweight and Obesity (web article). Release date: 07 July 2022. Available from: https://www.aihw.gov.au/reports/australias-health/overweight-and-obesity (accessed April 2023).
- Cifuentes L, and Acosta A, Clin Res Hepatol Gastroenterol 2022;46(2):101794.
- Guyenet SJ. The Hungry Brain. Outsmarting the Instincts that Make Us Overeat. 2017; Flatiron Books, New York, NY.
- Yu Y-H, et al. Obes Rev 2015;16(3):234–247.
- Gearhardt A and Schulte EM, Annu Rev Nutr 2021;41:387–410.
- Muller MJ, et al. F1000 Med Rep 2010;2:59.
- Stogios N, et al. Nutrients 2020;12(12):3883.
- Markovic TP, et al. Obes Res Clin Pract 2022;16(5):353–363.
- Acosta A, et al. Obesity (Silver Spring) 2021;29(4):662–671.
- Cifuentes L, et al. EClinicalMedicine 2023;58:101923.
- Vallis M, Clin Obes 2019;9(2):e12299.
June 2023. AU-2023-03-0102 Polls: AU-2024-06-0020. Date of approval Aug 2024
It’s time to put food in its place.
Taking the first step doesn’t have to be difficult. Get started on your way to weight loss:
Connect to a doctor online
Start an online consultation to receive weight management advice and a program that fits your needs.
Find a doctor near you
Complete a short questionnaire and get a personalised conversation guide for your doctor’s appointment. Next, easily locate a nearby GP for an in-person consultation.
Prepare for your next doctor visit
Already have a doctor you go to regularly? Fill out a short questionnaire and get a personalised conversation guide for your next doctor appointment.
Date of Approval September 2023.
Sponsored by iNova Pharmaceuticals (Australia) Pty Ltd
©2024 iNova Pharmaceuticals