It takes about four hours for the stomach to fully digest a meal and pass it along to the small intestine. Food passes through the small intestine in just four hours, zipping along at more than a half an inch per second. Inside the large intestine, it takes about eight to fifteen hours, traveling at a more leisurely rate.
Some foods will travel just a bit faster.
No steak is sitting in your intestines for a week.
Good luck on your diet. Try not to get discouraged if you don't lose anything any given week. You're going to have to eat less for the rest of your life to maintain any weight loss and as long as you're not gaining, you're doing great. Us woman sometimes go through spirts at certain times of the month when we don't lose much. I gain exactly 2 pounds, a week before my period, every single month.
The longer you keep track on fitday, the clearer the picture will become. Sounds like you're doing just fine. 8 lbs in 2.5 weeks is fantastic.