Hi and welcome:

Your question is very interesting. The short answer is the less you eat, the more weight you lose.

Having said that, the concept of ‘fast weight loss’ is a tough one.

I don’t know where you got ‘recommended calculation of 1500 calories day/375 on fasting days’, so I can only guess you have computed your personal TDEE as 1500 and have taken 25% of that to get your fasting day number. To illustrate my point, about the fastest weight loss possible for you (given your 1500 TDEE), would happen if you ate nothing, 0 calories, for a week. If you ate no food, you might expect over time to lose about 3 pounds a week.

You can see that reducing your non-diet day caloric intake would increase your weight loss, but it would be measured in just a few ounces a week. (Going from 1500 to 1300 would cut 1400 calories out of your weekly intake, or about 6 ounces additional weight loss.) You have to decide if eating less is worth it – no one can make that decision for you.

Here is some information that gives a bit more on how the math works: http://thefastdiet.co.uk/forums/topic/tdee-for-the-curious-or-why-dont-i-lose-weight-faster/

Good Luck!

This is not a fast diet it is a way of eating that includes fast days. Fast not speedy 😉
On average most of us seem to lose between 1 or 2lbs per week on 5:2 and sometimes we plateau and need to try 4:3 or alternate day fasting to wake our bodies up again.
Also some only have water or calorie free drinks on their fast days.
The joy of 5:2 is you can make it work for YOU so that it suits your lifestyle and you can eventually maintain a healthy weight and not fall into the ‘yo-yo-ing’ trap.

Hi restless1, If you’re desperate to up your weight loss a bit then you should calculate your BMR and your TDEE and make sure you eat OVER your BMR on non-fastdays. You don’t have to eat right up to your TDEE if you don’t want to and those few less calories will help your weekly calorie deficit and therefore your weight loss. You have to decide for yourself if it’s worth it to you.

You can also not eat at all on your fastdays if you like? Some people are doing that and the numbers are totally arbitrary on fastdays anyway(Michael just figured he’d find it difficult to manage long-term on no food on his fastdays, so he plucked ‘25% of your TDEE’ out of the air, based on a similar, but not quite the same, study in the U.S.).

Whatever you do – DO NOT eat less than your BMR on non-fastdays. Whenever you lose significant weight, remember to recheck your numbers to make sure your BMR & TDEE are still current (they change as you lose weight).

Tracy:

You seem to be intent on eating over BMR – ‘Whatever you do – DO NOT eat less than your BMR on non-fastdays.’ I don’t understand why.

If you are doing 4:3, you eat under your BMR three days a week. If you do ADF, you are under every other day. Doctors usually hand out standard reduced calorie diets of around 1500 calories 7 days a week. For many, that would mean eating under their BMR 7 days a week.

The general rule is that the less you eat, the more you lose.

Why shouldn’t a person eat less than their BMR?

I’m not a doctor or a nutritionist and if you have better sources of information and don’t want to take any notice of any advice I give that is totally fine by me.

The way I approach 5:2 is as a lifestyle change forever. I am sure there are diets where people eat less than their BMR every day and get results, I know that simcoeluv and some others on here don’t subscribe to the concept of ‘starvation mode’ and perhaps they have good reason for not doing so.

My preference for the ‘Never eat less than your BMR on a non-fastday’ rule is not so much to prevent anyone falling into ‘starvation mode’ as it is to prevent people treating this as a ‘quick fix’ diet rather than a longterm lifestyle change that is sustainable and comfortable to live with.

Most people coming to this diet have a LOT of weight to loose and overly restricting themselves on non-fastdays as well as the fastdays may make them despair of this as yet another ‘diet’. Eating comfortably somewhere between your current BMR and TDEE and having 2 (or 3) fastdays a week will give a nice steady, comfortable weight loss for most people and will allow them to still eat all of the foods that they like (in moderation). It becomes a healthy, sustainable new lifestyle rather than a faddy diet.

That is my reasoning.

@tracyj – I think you’ve explained well. I do believe in starvation mode, simply cos I’ve experienced it and what comes with it. IE gaining weight on what should be a normal diet.

Perhaps we’re all at different risks of getting it – but I’m surely one famine proof woman who’d outlast many others and *still* be overweight.

My personal opinion is why risk it, if you don’t need to. This is a lifestyle change, not a quick diet where speed is what counts.