| Let me show you how I know. Not with my opinion. I am not a doctor, and my opinion would not be worth much to you anyway. With a study instead, and a big one. |
| Researchers at the National Institutes of Health followed 43,722 American women, ages 35 to 74, none of them night shift workers. At the start, each one answered a plain question about her bedroom: did she sleep in the dark, with a small nightlight, with light coming in from outside the room, or with a lamp or a television on. |
| Then the women were weighed and measured, and about five years later the researchers came back to see what had happened. They also tracked how much each woman ate, how much she exercised, how long she slept, and how well. That last part is what makes this study worth your time. |
| What they found |
| Sister Study, 2019. Park et al., JAMA Internal Medicine. |
| The lit bedroom (they gained) |
| Women who slept with a lamp or a television on in the room were 17 percent more likely to have put on 11 pounds or more over those five years. |
| The dark bedroom (they didn’t) |
| In the dark rooms, that pattern did not show up. A small nightlight was not linked to weight gain either, so this does not mean pitch black if you need to see your way at night. |
| The link held after the researchers accounted for calories, exercise, and how long the women slept. |
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| In other words, the women in the lit rooms were not eating more or exercising less than the women in the dark rooms. They were doing the same things. The one thing that separated them was the light in the room. |
| Her willpower had nothing to do with it. Yours doesn’t either. |
| So how does a lamp on a dresser end up on your waistline? |
| Your body runs on a clock, and that clock is set by light. Cells at the back of your eye do nothing for your vision at all. Their whole job is to report the light level to a spot in your brain about the size of a grain of rice, and that spot tells the rest of you what time it is: when to make melatonin, when to burn sugar, when to store fat, when to get hungry. Light after dark tells it the day is not over. Melatonin stays low, the overnight work starts late, and your body clock and your kitchen clock stop agreeing with each other. Studies suggest that mismatch is what nudges the weight, not the extra handful of crackers. |
| That woman was getting the morning right and losing every single night. She never stood a chance. Neither did you, I would bet. |
| And that is the part no one says out loud… The advice you were handed was not wrong. It was half of it. |
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