This post was written by one of our contributors, phycology student – Ellie Wright
Over and under-eating are not symptoms of willpower (1, 2, 3). Mechanisms in our bodies and brains operate beyond our conscious awareness, interacting with our environment and genetics to determine how hungry we feel (2).
Understanding why we keep eating when full or why we don’t eat enough when we are lacking in nutrients or energy can help us rethink the food guilt, that some of us often experience.
Obesity affects many of us. In the UK, around 60% of adults and nearly 30% of children aged 2-15 years are overweight or obese (4). We can use knowledge about what drives our eating behaviour to help understand why obesity rates are increasing, and challenge why it is not simply down to “lack of self control”.
Science tells us that appetite is not accessible to introspection. This awareness can help us to use self-compassion to accept what our body wants. We can enjoy thinking about what food environment we want to make for ourselves to feed a joyful relationship with food.
Our biology: overeating
Most people who are obese are resistant to leptin (2, 3, 6). Leptin is a hormone which suppresses appetite and controls food intake over the long term (5). Without the action of leptin on the suppression of appetite, many obese people can experience hunger regardless of how much they eat (2, 3).
Leptin is produced by adipose (fat) tissue. It travels in our blood to the brain where it tells the brain information about our nutritional status so the brain knows when to halt hunger signals. Appreciating that appetite is controlled by this circuit which works beyond our conscious control, provides evidence for why how much we eat is not a symptom of willpower (2, 3, 6).
Food addiction: a diagnosis which experts want clarified
Diagnosing an inability to control eating with a label can help comfort people struggling with food intake and provide useful symptom classifications for clinicians (7). 88% of people diagnosed as food addicts are obese (8). A large overlap of binge eating and food addiction diagnoses is problematic. It can make it unclear which treatment patients would most benefit from. Some experts would like the questionnaire which diagnoses food addiction changed to clarify the relationship between addiction, binge eating and obesity (7, 9). They say understanding how psychological and physical diagnoses interact with each other may change what treatment is best for a patient.
Critics and supporters of food addiction agree that people without food intake control struggle to resist overconsumption, despite knowing the associated increased health risks (7). Supporters say activation of reward pathways, similar to those used in drug taking and subsequent compulsive eating behaviour, fits the definition of food addiction (7, 10, 11). But critics argue no single addictive substance has been identified as a chemical which causes this change from normal to addictive eating (7). Both sides agree overeating is a symptom of the bodies biological mechanisms operating beyond our control.
That dopamine hit: how food desire works
When we see food, our brains release dopamine. Often mistakenly called the pleasure chemical, dopamine is actually a chemical motivator, promoting a desire for things we do and do not enjoy (12). It can be part of both healthy and disordered eating (13). The balance of hunger hormone ghrelin and appetite suppressant hormone leptin, determine the impact dopamine has on our appetite (14). They work against each other to promote and prevent how much dopamine reaches the brain’s pleasure centres (14). The more dopamine in our reward centres, the more we want to consume that tasty treat!
It’s not just biology
Food intake is too important to be assigned our body’s hormonal systems alone. How hungry we feel is also a product of biological interactions with our DNA and environment.
Why we have an innate bias for energy dense foods
Food intake temporarily disrupts the body’s performance until energy balance returns to normal, for example, by rebalancing blood glucose levels (15, 16). This means that energy dense foods appear highly appetising because they have a relatively low-cost digestive impact. At 9 kcal/gram, fat offers a high energy reward, more than double that of protein and carbohydrate (which have 4 kcal/gram) (3, 17, 18).
Human’s feast or famine response, driven by historically unstable food supplies, increases how much our energy storage bias impacts our body shapes. In the Western world, our food environment tends to be stable and energy dense food is readily available in large portion sizes; this is known as an ‘obesogenic environment’ (3, 17, 18). Experts say a combination of this habitat with our fat storage survival instinct can partly explain the increasing prevalence of obesity – a mismatch between our genes and environment (2, 3). In the western world, many of us no longer have an unstable food supply that put us through these periods of famine and food excess. Awareness of the challenge our body faces when responding to highly appetising foods in our environment can motivate us to design our own food habitat, helping us to eat foods that we enjoy and make us feel good.
Genetics: It’s not just you, it’s your genes too
Despite an obesogenic environment, not everyone is putting on weight. Genetics account for approximately 70% of the weight differences between us (18, 19).
Twin and adoption studies can provide compelling evidence for DNA’s role in body weight. For example, a twin study found that the environment was not responsible for connecting the weight of adoptive parents with the weight of their adopted children (21). Further, weight similarities between this same group of adopted children and their biological parents, who they hadn’t seen since birth, was equivalent to weight similarities between biological parents who bring up their own genetic children. Still, the environment in which you surround yourself can influence whether genes get switched on or off. Appreciating the role of genetics as being 70% responsible for the weight differences between us is a powerful antidote to guilt related to body size.
Practical ways to help yourself feel good about food
Slow down! Eating in progress
Taking time to enjoy your food doesn’t just benefit your wellbeing, it also helps match your food intake to what your body needs. A recent pilot study used an fMRI brain scan to show that eating speed can predict how much hunger hormone ghrelin is suppressed two hours after a meal; slower eaters had less of the hunger hormone than faster eaters (22).
Use your biological psychology: senses and memory
When we take time to notice and experience what we eat, we give our brain sensory and memory signals which can decrease appetite (23, 24). For example, a study found amnesic participants demonstrated excessive eating, repeatedly consuming third servings, when they could not remember what or when they had eaten (23).
The impact of our memory on how much we eat, as well as the sensory experience of eating, was shown again in an experiment where participants were fed soup in three ways. The highest hunger ratings were experienced by those who were not aware they were being fed via a tube. Lower hunger ratings were recorded from people who were told when the soup was being inserted through a tube and by those who ate the soup normally (24). This suggests mindfully enjoying the sensory experience of eating and taking time to notice the appearance, smell, taste and texture of food can not only be pleasurable, but it can change how full the same amount of food can make you feel.
Build your own food environment
Experts say rising obesity rates are caused by an increasingly obesogenic environment (2, 3). Regardless of what weight we are or want to be, we can change what food we surround ourselves with. Our food habitats exist on and offline. Consider what types of food you want to see on your social media feed, what messages from brands and public figures you want to consume and where you take yourself for lunch. Be kind and buy food for days when you can’t be bothered, feel blue or just don’t have the time. And, eat with friends: sharing a meal is fun, encourages appetite to respond to memory and talking slows you down!
Reconnect with your body and others
Self awareness can help us to think about the positive impact that food can have on our body. Exercise motivated by weight loss alone might feel disappointing as it is often counteracted by increased food intake (3, 26). But, finding movement you like brings heaps of joy! Meditation and yoga keep me present and experimental findings suggest they develop self-regulation; awareness about our choices, habits, behaviour and emotions (25, 26). Connections with others, including human touch, can help reduce stress, lower heart rate, blood pressure and cortisol levels, whereas isolation is associated with higher levels of inflammation (27). Keeping stress to a minimum can help to reduce anxiety-fuelled thoughts and eating behaviour.
Self-compassion takes practise. Books offer guided loving kindness meditations (e.g. 28 – recommended to me by two NHS clinicians). These can feel a bit weird at first! But, give them a go, remembering that this is a skill that takes time to pick up. Doctors, friends, family and charities can help you to challenge any negative thoughts you might have around food, so reach out to them. Studies have shown that it is worth it! Having support networks can more than half the risk of mental illness (28).
Resisting what your appetite wants is incredibly difficult
Food is too important to be allocated to a single mechanism like willpower. Our appetite is complicated and controlled by many factors. Much of what we eat is a product of our psychology, biology, environment and genetics interacting with each other. This happens beyond our conscious awareness meaning how hungry we feel cannot be changed by introspection. Accepting this can help us to compassionately challenge food guilt and motivate us to shape our own eating environments with foods that help us to feel good in the body we have.
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