As soon as celebrities revealed that their secret to weight loss was not eating after 6 or 7 PM, tons of people jumped on the bandwagon thinking that this diet fad was the missing key to their weight loss goals.
For a while, it was believed that late night meals and snacking were preventing weight loss and even causing weight gain. What many failed to realize is that it’s about what and how much you’re eating – not at what time you’re eating. That is to say that weight gain does not exist in a vacuum. You’re body isn’t going to say to itself, “It’s 7 o’ clock, time to start converting all calories into fat!”
You gain weight when you consume more calories than you need. Many people who eat at night burst through their calorie limit and keep going. They probably also choose foods that aren’t exactly healthy, which means that they’re quickly consuming hundreds of unneeded calories.
One study found that the negative effects thought to be associated with nighttime eating aren’t necessarily consistent when people consume small, nutrient dense, low-calorie and/or single macronutrient meals. The study also found that obese participants who ate at nigh but also exercised did not experience the adverse effects thought to be associated with late-night eating.
Another reason why eating at night became associated with weight gain is the lack of sleep it causes. If you’re up eating, you’re not sleeping. Countless studies show that a lack of sleep leads to weight gain. A lack of sleep leaves you low on energy and slows your metabolism. When you’re tired, you don’t expend as much energy, which means you don’t need to consume as many calories. Moreover, with a slower metabolism, you don’t burn through the calories you consume as quickly as you would with enough sleep. So if you eat the same amount of calories when you’re tired as you do when you’re sufficiently full of energy, your body stores those unneeded calories as fat.
Conclusion: The hour of evening doesn’t affect how your body stores fat. It’s how much and what you’re eating. If you can have a healthy late-night snack, or at least refrain from over-eating, then having a snack at night won’t cause you to gain weight.