A fit woman holds her hands around her toned stomach
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It's a cruel trick our body plays on us: we wake up in the morning and look at our flat, almost unrecognizable stomach, only to watch it disappear as the day gets started. Experiencing this phenomenon isn't something that sets you apart from everyone else on the planet. It's actually a pretty common thing, and there's a scientific reason behind having a toned tummy in the a.m.

Joel Martin, Ph.D., C.S.C.S., assistant professor of kinesiology at George Mason University, talked to Shape about why your stomach looks so good when you wake up sometimes. That's because you've become dehydrated overnight and lost a lot of fluids.

When all that water escapes your body, it automatically appears as if you’re skinnier, and you might even see more muscle definition on your stomach.

This is even more likely to happen if you ate a healthy dinner the night before that wasn't packed with sodium and fat, because your body won't feel the need to retain water as much. Dr. Martin also pointed to the fact that, when you wake up, you haven't eaten for the last several hours, so your stomach isn't packed with heavy food. That's a major reason why you weigh a lot less in the morning than right before you went to bed.

Unfortunately, your morning abs will probably disappear, because the more you move around and the more you eat your body will hold onto water and you'll develop more gas and stool. The only way to keep flat abs is by maintaining a healthy diet and exercising regularly. But, hey, that almost-six-pack was fun while it lasted!