Exactly.

If you want something to last a long time, start it on the new moon. That includes keeping calories or poisons in your body. So if you eat more on the new moon, you'll get fat quicker then otherwise.

If, on the other hand, you want something to NOT last a long time, to get rid of it quickly, then start it some time after the full moon. Not on the full moon as that's a very stressful aspect, but rather a little later. Then poisons will leave your body faster.