Intermittent fasting and weight loss

How long has your weight loss stalled for? 3 days? 3 months?

Probable issue with water retention, would be my first guess, but it's a guess. Why I'm guessing that:

• You'd been losing super fast, 6kg (13.2lbs) in a month, so around 1.5kg (3.3lbs) per week, which is about 1.6% of your current weight per week.
• If you've lost that much in a month, then stalled suddenly - which I'm not sure is true, but consider probable based on how you phrased your post - then it's unlikely that you've found maintenance calories, and more likely that you're seeing water retention weirdness.
• We'd expect your daily calorie needs to maintain your weight, at your size/age, to be something above 1900 calories daily, and that's if you're quite sedentary. (If more active, you'd be expected to burn even more calories.) That would be about 13,300 calories burned per week.
• Eating 500 calories two days a week, and 1200 calories 5 days a week, you're consuming around 7000 calories per week. That would be a 6300 calorie weekly deficit and probably more, so at least a 47% cut from TDEE. If the 1.5 kg is actually the weekly average loss, that implies that your deficit is actually much larger than that.

Super-fast loss causes stress, and stress tends to increase water retention. Stalls on the scale are frequently water retention, and sudden stalls highly likely to be that.

If your scale stall is caused by water retention, waiting it out is the answer. The scale is likely to drop within 4-6 weeks at the outside, possibly quite suddenly. That's unless your ultra-extreme loss tactics cause enough fatigue to significantly reduce calorie expenditure. While ultra-low calories are likely to do that eventually, it's soon to see that if you've only been doing this for 6 weeks or so as I'm inferring.

Super-fast loss can also do things like cause muscle loss, hair thinning/loss, supression of the immune system, and more . . . some of the potential impacts much worse, too. In addition, very commonly the body will eventually fight back against super-fast loss via hunger/appetite hormones. When that happens, the frequent outcome is bouts of deprivation-triggered over-eating, breaks in the action, or giving up altogether because the extreme process becomes just too hard.

The standard way of doing 5:2 intermittent fasting is to eat at maintenance calories 5 days a week - that 1900 or more, in your case - and 500 calories on two non-consecutive days. 1200 calories is the lowest number of calories MFP will ever recommend a woman eat, even petite older women who have lower maintenance calories than someone your age/size. (For other USA-ians like me, you're around 5'9" and 200 pounds.) MFP makes 1200 the low-end limit because it's very, very difficult - nearly impossible - for any adult woman to get basic adequate nutrition on lower calories.

It's probably obvious that I think you've adopted a riskily extreme approach. I'd encourage you to give it a re-think. Faster weight loss isn't better weight loss. Fast weight loss can be a trap. I'm saying that as someone who accidentally lost too fast at first myself - eating 1200 plus all exercise calories 7 days a week - when around 10 cm shorter, 8 kg lighter, and 10 years older than you are. I corrected as soon as I realized and ate more, but still got weak and fatigued and took multiple weeks to feel like my normal self again. No one needs that.

No matter what you decide, I sincerely wish you success with your goals. The quality of life improvement from reaching a healthy weight (and staying there long-term) is huge - at least it was for me.

Best wishes!

Yes, please try to eat more. Eating more will be more health-promoting, and more likely to be something you can continue long enough to lose a meaningful total amount of weight. Yes, weight loss will be slower, but it will be better for your health and energy level.

MFP will not recommend calories as low as 1000. It won't recommend anything below 1200 for women, 1500 for men. At below 1000 calories logged, it will start warning you in various ways that you're eating too little. I think that's what you're describing. It doesn't mean everything is good down to 1000 calories for everyone, it means that anything consistently below 1000 calories IS bad for virtually everyone.

You're relatively tall for a woman, not petite. You're not old. 1200 calories may be a suitable number for some women, but they tend to be short, older than you are, and quite inactive, probably without much weight left to lose besides. It's a myth that all women need to eat 1200 calories to lose weight.

There are a couple of common rules of thumb people suggest around here about a healthy, sustainable rate of weight loss.

One recommendation is to lose no faster than 0.5-1% of current weight per week, with a bias toward the lower end of that unless severely obese. Technically, you are in the overweight BMI range, not obese, let alone severely obese. That range for you would be 0.455 kg to 0.91 kg per week, call it half a kg to 1 kg. Closer to half a kg would be better.

Another recommendation is to cut no more than about 20% below the number of calories you burn each day. You can use a calculator like the one below to get a nuanced estimate of the total number of calories you burn daily. That's called TDEE, total daily energy expenditure.

https://www.sailrabbit.com/bmr/

Just as an example of the arithmetic, not as a personalized calorie goal for you, let's say someone's TDEE is 2000 calories per day. Using this rule of thumb, they would eat 20% below that, which is 1600 calories per day.

(There might be some exceptions to the above rules of thumb for people who have a medical urgency requiring weight loss AND who're under medical supervision for nutritional deficiencies or health complications. That case would be one where their doctor actually tells them to lose faster. Some doctors hand out 1200 calorie eating plans. That's usually with the expectation that people will go above 1200 in reality, because it's common for people not to comply with diet plans.)

Here's what I'd recommend:

Put your demographic information into MFP, tell it you want to lose half a kg per week, get its calorie recommendation. It will probably be at least 1400-1500 calories per day, maybe more. Eat close to that recommendation for at least a month, see if you average around half a kg loss per week. If so, you're all set until it's time to slow loss down a bit when you're lighter. If not, adjust your calorie goal using the assumption that 1100 calories per day is about a kg per week, using arithmetic for partial kg adjustments.

If you like intermittent fasting, it's fine to do that. You can set up your weekly plans any way you like (within reason) that averages out close to your MFP calorie goal over each week. If you keep 2 days at 500, increase other days a bit to get the right weekly average.

I'm troubled by your saying that you think you may be addicted to feeling hungry, and feel uncomfortable if you aren't hungry. I read and understand COGypsy's comment about how lithium side effects could lead a person in that direction. Still, I'm worried that somehow deep inside you've internalized a common feeling in our culture, the idea that being overweight is a character fault or sin, and that we need to punish ourselves with suffering in order to reverse that. That's not true. That's not a path of thriving.

If you ask me, the really big prize on offer here is not just losing the weight we want to lose, but staying at a healthy weight long term, ideally permanently. (For me, doing that has brought big quality of life improvements.) Many people find staying at a healthy weight more difficult than losing. Staying at a healthy weight depends on finding new permanent habits we can stick with when other parts of life get challenging . . . because they will, eventually. Being hungry all the time isn't compatible with that long-term goal for most people.

I'm wishing you health plus success with your goals!