The varying pull of the moon causes tides, and it may also affect how much you weigh - though hardly so much that you'd need a smaller swimsuit.
Anything that's going to change the gravity field will change your weight. That's because your weight is equal to the mass of your body multiplied by the local acceleration of gravity.The reason your weight changes is not because of the ocean tide, but because of the solid Earth tide. When the tide pulls you farther from the Earth's center of gravity, you weigh less than when the tide is elsewhere on the Earth and you are closer to the Earth's center.
But don't give up your dieting regimen just yet. In fact, you wouldn't see any difference on your scale. The variation would be trivial - something like the difference between inhaling and exhaling.
If you want an exact estimate of how much less you'd weigh, consider this estimate: Your weight would change by less than one-millionth of its total amount.
- Usha Lee McFarling