Do you eat under the calories you should on non fast days? I had my first fast day yesterday and actually felt fine. Kept considering a biscuit but realised I wasnt wanting it for hunger so managed to resist. Today I've logged 800 calories and that includes dinner - should I make myself eat more?
You are supposed to eat at your TDEE (if you check on the 5:2 website, they have the calculator there or just google TDEE calculator) - this will provide you with the number of calories that you need on a daily basis to maintain your weight and the general view is that you should be eating these on the 5 non-fast days.
If you ate 500 calories yesterday and then only 800 calories today, then that isn't really the 5:2 diet, it is a very low-calorie diet which is not the aim of this.
Don't worry, a few people do find fasting takes away their appetite the first week, but it soon returns. A week or so on v low cal won't cause problems, if you are not deliberately starving yourself. After 2-3 weeks, most folk have adapted to fasting and settled down. Do post on the main thread if you need more support.
Many people naturally eat a few 100 cals below TDEE on the weekday NFDs, then eat a lot more at the weekend. Some find that they gradually adopt more healthy habits, without making a big deal of it, just listening to their bodies - don't worry that your body said "cake" today; it may be saying "spinach" next week