When I was going through the absolute worst period of my life, I was thinner than I’d been in decades. “You look great!” friends said, joking that the “divorce diet” agreed with me. I chuckled ruefully, because they weren’t trying to be jerks, but all that anxiety and fear and stress I felt for my children and my future filled up my stomach, leaving no room for food. It was no joke. Never mind that diet culture, which pushes the idea that thinness is the be-all-end-all and makes you a superior human, harms everyone. I didn’t feel good, emotionally, or physically. My weight loss was an alarm that my body and mind were sounding.

And that’s how it goes with stress. Whether it’s due to a major crisis like a divorce, death (or oh, I don’t know, a global pandemic?) or something more every day, like a deadline or a new job, acute stress does wonky things to your body.

That’s due to the classic fight or flight (or freeze) reaction, says psychologist Kasey Goodpaster PhD. Even if no one is trying to physically harm us, these life events feel threatening to our bodies, requiring us to be ready for action. “Our bodies are programmed to prioritise survival by preparing to fight off or run away from threats, resulting in muscle tension, increased heart rate, and increased respiratory rate,” says Goodpaster. “During the fight-or-flight mode, other bodily functions such as digestion are slowed, so GI motility decreases, which could account for changes in appetite,” she says.

How does stress cause weight loss?

Though stress can cause weight loss, it doesn’t for everyone, and more often, stress causes weight gain or no change at all, says psychologist David H. Rosmarin PhD.

“If people are super busy and stressed out or going through a traumatic situation or feel like they’re totally underwater,” that’s when weight loss, if it occurs, takes place, says Rosmarin. “When you’re really gunning it, you don’t have time to eat and you don’t have the appetite to eat.”

Goodpastor explains, “When one eats much less than usual, perhaps due to skipped meals when stressed, it can cause the metabolism to slow down. The body essentially goes into “starvation mode,” stores fat, and eats away at muscle, which leads to short-term weight loss.

Why stress causes weight loss sometimes and not others

The kind of stress you’re being slammed with may also point to whether you’ll gain, lose, or show no weight change. That’s because there’s a difference between the type of act-right-now acute stress and the chronic, grinding stress that hits you when, say, you’re in a long-term caregiving situation or perhaps an abusive relationship in which you’re always on guard. “Appetite is often reduced during acute stress, whereas chronic stress has been linked to increased food cravings and weight gain,” says Goodpaster. That’s not a hard and fast rule, though, and some studies show that people with higher BMIs are more likely to gain weight when stressed, and those with lower BMIs are more likely to lose weight when stressed. No one knows for sure why that is, but one of the systems in the body that is affected by stress is your endocrine system, which regulates hormones. “Hormones at play include cortisol (the stress hormone) and ghrelin (a hunger hormone that motivates food intake),” she says.

Plus, the way you deal when you’re stressed is in part learned over time, says Rosmarin. For example, if you’re someone who grew up in a house where giant bowls of pasta brought you comfort, you might be more likely to eat more when something stressful happens. But if you learned to cope by distracting yourself, running marathons, or ignoring your hunger, you may “forget” to eat, and so not take in enough kilojoules. “Human choices and behaviours are a big deal,” says Rosmarin.


So when should you worry about weight loss due to stress?

Most of the time, it isn’t a major cause for concern. “Typically a change of less than 4.5kg or 5% of body mass isn’t considered clinically significant, because most people’s weight naturally ebbs and flows within a range, rather than being a fixed number,” says Rosmarin.

Plus, when things calm down, your body usually goes back to normal functioning and your appetite, or desire to eat, returns. “When eating returns to normal, because there is less muscle to burn kilojoules, the weight can come back quickly,” Goodpastor says. As your life stabilises, your weight likely will too.

How to avoid weight loss (or gain) from stress

It’s about self-care and being kinder to your body, says Rosemarin. Here’s what you can do:

  • Exercise: That means moving your body more, by walking or doing whatever you enjoy most.
  • Get regular sleep: Sleeping for 7-9 hours per night is ideal.
  • Eat at regular intervals: Yes, even if your appetite is less than robust.
  • Connect with others: Isolation is hard on your body. “Actually connecting with people emotionally, whether it’s family or a close friend, is really key,” Rosemarin says.

When to talk to your doctor about unexplained weight loss

If you’re losing weight when you’re under stress, but it’s just a couple of kilos, focus on getting through the stress and taking care of your body. Here are signs, though, that you may need to see a doctor:

  • You’ve dropped more than 5% of your body weight without meaning to, or around 4.5kgs.
  • The weight loss is happening alarmingly quickly.
  • You’re experiencing digestive problems, such as diarrhoea.

Your doctor will want to rule out or treat you for depression, anxiety, or other mental health issues, all of which could lead either to weight loss or gain, says Goodpastor. If it’s a medication that’s causing weight loss, you might need an adjustment, and if you are facing food scarcity or economic distress, she may be able to refer you to an organisation that can help.

And of course, stress can and does trigger or exacerbate existing eating disorders, such as ARFID or anorexia. ARFID stands for Avoidant/Restrictive Food Intake Disorder, which is extreme picky eating that gets worse over time and that has nothing to do with wanting to lose weight, but nonetheless results in a person (often a child) not eating enough. “ARFID can be pretty bad and I’m sure you know anorexia is downright dangerous,” says Rosmarin. “The bottom line is persistent failure to maintain an adequate weight requires professional intervention.”

The takeaway: Take care of yourself

If you’ve lost a lot of weight without trying, whether you’re stressed or not, head to the doctor. But if you’re not underweight and it’s just a few kilos, don’t worry—it will likely come back when you eat normally again. “Less than 4.5kgs is usually not a big deal from a health perspective,” says Rosmarin.

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