A quick question - in the calculation around calorie intake / exercise to burn off calories etc., should there be some note taken of waste products? For example, if I eat a biscuit which contains (the packet tells me) say 100 Kcals, would that all remain in my body, or would some of the calories be excreted in due course?
Don't sweat such details as how much will pass in the gut, unless a food has a large undigestable fiber content. Eat a great variety of foods and eat less of it and let your scale tell you if the amount less you have chosen is enough. Use calories as a general guide to make that first decision of how much less to eat,ie. 300 less a day per week is around a pound. Eat whole grain foods and beans and fruits and veggies of all kinds and lean meats and fish to make sure your calorie reduced diet is also providing the nutrition you need. Weight loss can be irregular,ie. variation in the rate of loss with the same amount of foods. If you are not losing, not to exceed around 2 lbs per week, then eat less of everything until the rate increases.