Does stress slow down your metabolism?

Dr. Cabral describes the thyroid as the body's thermostat. Stress can come from outside the body, like poor sleep or stressful relationships, or from inside, like gut issues, inflammation or pain. All of it pushes up stress hormones, and when that stress is chronic, he says thyroid output goes down over time. That's why, in his view, the body often handles a 21 to 28 day crash diet fine and then slows. Once that happens, he says you burn fewer calories both during exercise and at rest, so the same amount of food can lead to weight gain. He mentions this can show up in lab work, which is a conversation to have with your doctor.

He also treats extreme dieting as a stressor in itself. He points to a follow-up on Biggest Loser contestants who, years later, could eat roughly 500 to 700 fewer calories a day. He still believes in a calorie deficit, but says mass deprivation combined with high exercise output is a recipe to crush your metabolism. His alternative is proper macros, exercise customized to you, and attention to sleep, hormones and overall health.

Nikkiey brings it down to everyday life. If you've had weeks where the scale stalls or you feel extra bloated even though your food and workouts haven't changed, she says stress is often the main reason. Something as small as a time change that throws off your sleep can add up. She explains that cortisol stores body fat, and lists the usual culprits: not eating enough, not sleeping well, not drinking enough water, and thinking negatively about your body.

So if your progress stalls during a hard stretch, that isn't a lack of willpower. Stress is a real variable, and a good plan accounts for it instead of asking you to diet harder.