Eating in moderation and maintaining a lean body is a goal shared by many of us. However, our minds often betray us, even when our stomachs are clearly full. While we know what to do and understand which foods to avoid, we struggle to resist them. But how does this happen?
According to Stephan J. Guyenet, a neurobiologist and well-known obesity researcher, our brain controls our eating habits. It’s our primitive instinct to eat any food in sight to survive in a world with limited resources, an environment that no longer exists for most of us.
In “The Hungry Brain,” Guyenet reveals refreshing insights on the field of nutrition and brain-gut correlation. His comprehensive explanations, backed by extensive scientific studies, shed light on our impulsiveness to overeat and our struggles to lose weight. Tidbits of enjoyable evidences are spread across chapters, they are enlightening and provide a new understanding of our relationship with food.
Fated to be Fat
Genetics takes responsible in obesity. Some people are so genetically resistant to obesity, some others are so genetically susceptible that they may carry excess fat even in a healthy environment. For the rest of us, the environment in which we find ourselves has a major impact on our weight.
As Francis Collins, a geneticist and director of the National Institutes of Health, said,“Genetics loads the gun, and environment pulls the trigger.”
Mental Battle of Weight Loss
What happens when weight-loss progress stuck?
When we have successfully lose some weight, our body require less calorie intake to fuel our activities, the calorie deficit gradually closes, and weight loss stuck.
How to break a stuck weight loss?
We have to reestablish a calorie deficit.
Why is it so easy to gain fat after a cut?
Weight loss → triggers mental and biological reactions to regain the lost fat by several mechanisms:
- brain alleviates the activity of the sympathetic nervous system and decreases thyroid hormone levels → retard the metabolic rate by decreasing our body’s temperature and activity. This is why people who have lost some weight become more sensitive to cold and sluggish.
- decreasing the number of calories burn in physical activity.
- the brain sends signal to crave high-calorie foods.
- hypothalamus ensures that we take more food to feel full at a meal than it did before we’ve lost fat. Our brain dampens the feeling of satiety so we won’t feel satisfied until we have eaten enough calories to start regaining fat
How could we crave something that we see on screen?
The process why we crave something just because we look it on our phone or television (or any kind of) screen is because of a phenomena called Pavlov conditioning.
It was founded by Ivan Pavlov, one of the first scientist to reveal how animals study to link neutral cues with food. As we have trained that the vision and get a sniff of certain food foresees a fatty, starch reward in our stomach and supported by the availability of dopamine, those sensory stimulate our excitation to eat food.
Brain, the appetite controller
Hypothalamus as lipostat, the regulator of appetite and body fatness
For this role, hypothalamus is also called the body’s lipostat. The functions are:
- to accept information about the size of fat stores from various signals, such as leptin
- to synchronize the our mental and behavioral responses to defend adiposity
- to maintain our energy balance
What is leptin?
- Leptin is adiposity factor in our body.
- Lack of leptin → obesity risk
- Leptin-deficiency in children → children always hungry, have a strong emotional and cognitive attachment to food
How does leptin regulate the hypothalamus?
- Leptin turns off neurons that encourage us to eat
- Leptin turns on neurons that hinders us to eat
How food causes changes in the hypothalamus?
- When we eat too much food for several days, our leptin levels upsurge and trigger desensitization of our brain circuits that respond to leptin. However, high leptin levels are not enough–the hypothalamus has to be “hit” for the second time for elevated leptin to increase the set point of lipostat. This second hit could lead to changes in brain.
Leptin resistance
Someone with leptin resistance has to overeat to feel the same satisfaction that a lean person feels after eating a smaller meal.
It means that the diet program will be much harder since it challenges us to fight deeply wired impulses. However, there is still hope, but keep in mind that it is essential to understand, honor, and work with what you’re up against.
How to fight ourselves to lose weight?
- Do not eat high-calorie food
This kind of food accelerates our progress to be an obese person by unconsciously eating it too much and switching lipostat at a higher level.
- Focus to eat low-calorie and less rewarding food
As we eat this food, our lipostat will not fight us as vigorously.
- Do more intense exercise
High intensity of physical activity may help us to avoid weight gain, speed up fat loss, and preserve that loss.
Sleep and weight loss
How much sleep do we need?
We do not have to follow the book by sleeping seven to eight hours a day. We have different needs of sleep so sleep as much as we need to fully restored our body.
How does lack of sleep intensify food consumption?
Lack of sleep leads to:
- parts of our brain responsible for food reward become more active → rises the brain’s perception to food, specifically high-calorie foods.
- impair cognitive functions and lipostat that sense the body’s energy status and sets our motivation for food
Adults who sleep less than 6 hours have higher risk to gain weight over time and correlation between short sleep and weight gain is strong in children.
How does stress affect food intake?
A lot of anecdotes has been spreaded that stress decreases appetite, reduced food intake, and weight loss. However, what actually happen is the other way around.
Amygdala is the part of our brain that reacts to external and psychological stress. Under stress condition, amygdala send signals to brain stem → activate sympathetic nervous system and followed by:
- pulse and breathing rate quicken
- blood pressure rises
- palm sweats
- digestion slows
- blood flow to muscle increases
- rising levels of sugar and fat in bloodstream
Simultaneously, the amygdala sends a signal that causes the release of cortisol, a stress hormone to:
- increase blood levels of sugar and fat, similar to those of the sympathetic nervous system above, but on a slower and longer time window → maintain the high metabolic demands of dealing with a stressor for a long time
- suppress immune function
- rise food intake
The correlation of stress and weight loss
- uncontrollable stress → cortisol-raising effect → driving overeating
- Junk food simply makes us better emotionally
- Stress doesn’t just change the number of food we eat, it also alters the types of food we eat. In rat experiment, sugar and high-fat food helped rates feel better in the face of stress.
Outsmarting the hungry brain
- Fix our food environment. Get rid of all tempting, high-calorie foods that are easy to grab. Create effort barriers to sting
- Manage our appetite. Pick foods with high satiety but contain a moderate number of calories, such as simple foods that are closer to their natural state. Keep our body comfortable and realistic to our target weight: take more protein intake and limiting highly rewarding foods
- Sleep enough.
- Move our body to increase the number of calories expenditure. When people with excess weight exercise regularly, their calorie intake tends to go up, but usually not enough to compensate for the calories they burn.
- Manage stress well.
Author: Stephan J. Guyenet, Ph.D.
Genre: non-fiction
Publication date: 7 February 2017
Publisher: Flatiron Books
Number of pages: 304 pages
