1. It Affects Your Hunger Levels More Than You Thought
Just thinking about a stressful event in the future (like figuring out how to care for aging parents or talking to your boss about your overdue raise) increases levels of ghrelin, the hormone that tells your brain that you want some food now. You're probably not craving cauliflower, either, and here's why: Eating comfort foods really does reduce the amount of stress you feel, according to a study in Appetite.

2. It Might Stop Your Body From Breaking Down Fat
Normally, the fat you eat gets used for energy. When you're under chronic stress, an enzyme that helps that process along doesn't do its job, found a recent study on mice in Molecular and Cell Biology of Lipids. A protein your body produces in response to the stress blocks the enzyme, so that fat gets stored instead. The researchers think the same thing may happen in humans.

3. It Zaps Your Energy During Workouts
When people did mental work in the middle of a physical task (like doing a morning HIIT workout while also thinking about a long to-do list for the day), their muscular endurance decreased by 25 percent, found one study. Lead study author Ranjana Mehta, PhD, assistant professor of environmental and occupational health at Texas A&M University, did a similar follow-up study using brain scans to figure out why cognitive work leaves us physically spent sooner. She found that doing mental and physical tasks simultaneously exhausts your brain faster, and since your brain sends signals to your muscles telling them to keep working, when it's tired, your muscles feel fatigued too.

4. Your Eating Plan Goes out the Window—and There's a Scientific Reason Why
There are certain areas of your brain that log your long-term goals and nudge you toward choices that'll help you reach them. Short but intense bouts of stress (the kind you feel during a single nerve-wracking event, like giving a speech or taking a test) make those areas less effective at their job, according to research in Neuron. At the same time, if you're trying to choose what to eat, your brain zeroes in on the immediate satisfaction you get from biting into, say, a cheese Danish over a veggie omelet. Delicious but not so nutritious choice: 1. Your self-control: 0.

The Stuff You Already Know (but a Reminder Can't Hurt)
—Work stress keeps a lot of us up at night, and a poor night's sleep also increases levels of your I'm-hungry hormone while lowering levels of leptin, which tells your brain you're full.

—When you're stressed, you have higher levels of cortisol, and cortisol leads to added pounds in your abdomen.

—Hectic days can lead to skipped meals (we've all been there—realizing it's 4 o'clock and you haven't eaten lunch), which slows your metabolism. Research in mice also suggests that it can lead to weight gain in your stomach, specifically.


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