If you’ve had unwanted weight gain or loss during the pandemic, you’re not alone. According to a survey by the American Psychological Association, 61% of American adults have reported unwanted weight changes since the start of the pandemic.

The results, published in March 2021, showed that during the pandemic, 42 percent of respondents gained unwanted weight (29 pounds on average) and nearly 10 percent of those people gained more than 50 pounds. On the other hand, nearly 18% of Americans said they experienced unwanted weight loss, with an average loss of 26 pounds.

I am a nutritionist neuroscientist and my research investigates the relationship between diet, lifestyle, stress, and mental distress such as anxiety and depression.

The common denominator of changes in body weight, especially during a pandemic, is stress. Another survey conducted by the American Psychological Association in January 2021 found that about 84 percent of American adults had experienced at least one emotion associated with prolonged stress in the previous two weeks.

Fight, escape, and food

The fight or flight response is an innate reaction that has evolved as a survival mechanism. It allows humans to react quickly to acute stress, such as a predator, or to adapt to chronic stress, such as food shortages. In the face of stress, the body wants to keep the brain alert. It lowers the levels of certain hormones and brain chemicals to reduce behaviors that don’t help in an urgent situation and raises other hormones that will.

When under stress, the body lowers the levels of neurotransmitters such as serotonin, dopamine, and melatonin. Serotonin regulates emotions, appetite, and digestion. Therefore, low serotonin levels increase anxiety and can change a person’s eating habits. Dopamine, another feel-good neurotransmitter, regulates goal-oriented motivation. Decreasing dopamine levels can result in less motivation to exercise, maintain a healthy lifestyle, or engage in daily activities. When people are under stress, they also produce less melatonin, the sleep hormone, causing sleep problems.

Adrenaline and norepinephrine mediate the physiological changes associated with stress and are elevated in stressful situations. These biochemical changes can cause mood swings, affect a person’s eating habits, reduce goal-oriented motivation, and alter a person’s circadian rhythm.

In general, stress can throw your eating habits and your motivation to exercise or eat healthy, and this year has certainly been a stressful year for everyone.

Easy calories, little motivation.

In both studies, people self-reported their weight and the researchers did not collect any information on physical activity. But it can be cautiously assumed that most weight changes are due to the increase or loss of body fat.

So why have people gained or lost weight in the past year? And what explains the dramatic differences?

Many people find solace in high-calorie foods. This is because chocolate and other sweets can make you happy by boosting your serotonin levels in the short term. However, the blood removes excess sugar very quickly, so the mental boost is extremely short, leading people to eat more. Eating to feel comfortable can be a natural response to stress, but when combined with a lower motivation to exercise and eat low-nutrient, high-calorie foods, stress can lead to unwanted weight gain.

What about weight loss?

Simply put, the brain is connected to the gut through a two-way communication system called the vagus nerve. When you are stressed, your body inhibits signals that travel through the vagus nerve and slows down the digestive process. When that happens, people experience realization.

The pandemic has left many people confined to their homes, bored and with too much food and little to distract them. When you add the stressor to this scenario, you are in a perfect situation for unwanted weight changes. Stress will always be a part of life, but there are things you can do, such as practicing positive self-talk, that can help you avoid the stress response and some of its unwanted consequences.