To steal from Michael Pollan: Eat food, not too much, mostly vegetables.

And I've gotta say 8 lbs in your first 3 weeks is not "too much" weight loss, considering where you started. And I agree with a previous commenter mentioned mentioned sodium intake can have much to do with it. When I quit salt - cold turkey - I lost 15 lbs (and my migraine headaches, praise the Lord) in two weeks; while not particularly active.

Shortly thereafter I took up biking and seems like everything I lost, I got back at the dinner table and in leg muscle mass. After the migraines went away, I became less selective about my diet, but kept the salt at a manageable level. I'd probably lose ten more if I quit meat or booze altogether.

If you continue to lose 8 lbs every month, then you can start to worry. Seriously doubt you're going to have that problem.