I lasted one week. The fasting days were just horrible for me and I could literally think about nothing other than food (or lack of) all day and it made me grumpy.

I did lose about a 1lb that week, but after I stopped it, I just started eating 1200-1400 calories a day, which works really well for me and I still lose 1b a week.

I know it works well for some people though and it has a lot of good benefits, so good luck!

Its really common for women not to be able to fast. Different hormonal responses and what not. Also - that's a very low intake for someone your age and height who is also exercising. I would really encourage you to try for a slower rate of loss, from a health and wellness perspective.

Thanks. I'm interested to know why your husband doesn't think 5:2 will be sustainable?

Not eating 2 days a week, for the rest of your life? I mean I'm sure there is a very small contingent of people out there who can do it, but for most people, no. Not even remotely feasible as a lifelong plan, no matter how you feel in this first few weeks. Its also somewhat debilitating to his fitness goals, as he really can't do anything strenuous on the fast days. He did on the first few, but now they are taking their toll.

Look at it this way:
Lets say you maintain on 2,500 calories a day. so your weekly maintenance is 17,500
Most people on MFP or any diet, decide that they want to lose say, 1lb/week, so 3,500 calories divided by 7 = eating 500 less a day. So they eat 2000 every day.

But on 5:2, you eat your normal food (assuming you have not been gaining or losing weight on that diet, 2500/day) and now you are eating only 600 on 2 days. So that's a deficit of 3800 calories per week. In other words, roughly 1lb/week.

Now lets say you get to goal weight, and your maintenance is now 2300 cals/day or 16,100. (in this scenario you either raised your activity level or you didn't have much to lose, but you look like you don't have much to lose)

so you are still eating 2500 a day, except 2 days a week you are eating 600. Now you've got a 200 calorie surplus, 5 days a week (+1000 calories) but you've still got a 3400 calorie deficit on the other 2 days, add it together, you're still eating a 2400 calorie deficit every week. so now you're either going to keep losing weight, or you will need to figure out a way to make up the calories, most reasonably I think by adding 1200 calories back to your 5:2 days, giving you 5x a week at 2500 and 2 days a week at 1800.

^^ perfectly reasonable but not exactly fasting.

But all of that assumes you don't start compensating for your fast days by allowing yourself more treats on eating days - Nick says he's already started to say to himself "well you can have a __________ today, you fasted yesterday." change all numbers accordingly, if you start doing that.

I know they make the diet out to be some kind of fasting magic, and there ARE studies that show interesting hormonal things that happen to men who fast (no studies on women), but that is minor minor stuff compared to the fact that you just plain aren't eating as many calories as you were before.

Oh MY GOD I WROTE A NOVEL AGAIN.

Anyway. I think its a lot more sustainable long term, to say, swap out one of your high calorie foods or snacks a day for a lower calorie snack, remove those 200 calories from your normal daily diet, and let a bit of exercise do the rest of the work for you (dropping the 200 calories and having a 30 minute walk daily should get you to the hypothetical goal I just made up).

And then for the rest of your life, you can either keep up the walk, or keep up the low-cal snack, and probably maintain your weight quite easily.