I’m confused about what’s happening, which is frustrating. I usually avoid the scale to stay positive, but a week ago I clocked in at 135 lbs at 5’5". Over a 19-day span (Aug 31 to Sept 18), I did full water/tea/black coffee fasts for 11 days. For the remaining 8 days, I either did one meal a day or ate within a 4-8 hour window. My intake on eating days was roughly 1500-1700 calories, focusing on high protein and low carbs. I also hit 10k-15k steps daily, which should have created a solid deficit. However, looking at photos and how my clothes fit, I see almost no change after nearly three weeks. What’s the deal? I’m feeling pretty let down and wondering if extended fasting is even worth the effort. Any advice? Have I damaged my metabolism?
I’m not sure, but consuming 1,500 to 1,700 calories for someone your size isn’t really a deficit. Even though you fasted for 11 days, you ate enough on the other days that your body likely clung to its reserves. How is your body composition? 135 lbs is a healthy weight for your height; you might see better results from strength training instead of more fasting. Increasing muscle would boost your baseline calorie burn, making future fasts more productive.
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I’m no medical professional, but here’s my take. When discussing metabolism for weight management, we look at BMR (basic functions like keeping your body temp at 98.6), EAT (planned exercise), NEAT (daily movement like walking to the fridge), and digestion (protein burns more). You upped your exercise but likely moved less subconsciously (NEAT), which is common when dieting. On eating days, the high protein helped calorie burn, though that stops when fasting. Your BMR is likely fine since you’re functional, though it might dip slightly in a deficit. Calculators suggest your maintenance is around 1600 calories, so you basically broke even on eating days and burned about 17,600 calories (roughly 5 lbs of fat) during the fasts. At your size, 5 lbs might not be visually obvious yet. You might also be holding water due to stress. If you aren’t eating and you’re still breathing, you are losing fat. Metabolism ‘damage’ is mostly a myth unless you’re an elite athlete at dangerously low body fat levels; your NEAT and BMR will bounce back quickly once you eat at maintenance.
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The body reacts differently to fasting versus starvation. In a true fast where you consume nothing, your system burns fat for fuel without slowing your metabolism, usually losing about a pound a day. Starvation happens when you eat very little, causing the body to panic, conserve fat, and slow down the metabolism to survive. This can actually lead to weight gain. Either commit to a full fast or eat properly; don’t just under-eat, or you’ll get the opposite of the results you’re looking for.
Honestly, 1500-1700 calories is quite a bit for your height, particularly if your muscle mass decreased during the fasts. Are you lifting weights? Losing muscle lowers your metabolic rate, and that calorie range might actually be maintenance or a slight gain for someone with low muscle mass. Do you use a scale for your food? It’s easy to miss hidden calories in things like oil or drinks. Also, try weighing yourself once a week—naked, after using the bathroom, on an empty stomach. Keeping a log helps you see the downward trend even when it feels slow. I’ve had months where I only lost a pound, but over six months, that adds up to a significant change for a slim person.
It takes way longer than a few weeks to actually damage your metabolism. Usually, the body just adapts unless there’s an underlying health issue. People only really need reverse dieting after months of extreme restriction. In your case, this is likely just in your head. Start tracking your weight daily so you have real data before worrying. If you want to keep muscle while losing fat, you should start lifting. Otherwise, you’ll lose muscle along with the fat. Assuming you lost 0.5 lbs per fasting day, that’s 5.5 lbs lost. Your eating days might not have been at a deficit. Still, losing over 5 lbs in a month is great progress. Stick with it for a few months to see the visual transformation.
Maybe take a break from fasting for a bit. That worked for me. Hormones can be tricky. I recently did a two-week juice fast and didn’t lose an ounce. I stopped, ate normally for three weeks when I felt hungry, and even though I wanted to fast, my body wasn’t having it. Now that I’ve started again, the weight is coming off. Stress and cortisol from things like heavy walking can stall progress, especially if your body is sensitive. Your metabolism is probably fine; it’s likely just stress. Plus, you aren’t overweight, so your body might just be focusing on internal ‘housecleaning’ rather than dropping pounds.
I dealt with the same thing, so I switched to longer fasts without the refeed periods, and that finally got the scale moving again.
The issue might be that you’re already at a healthy weight, so changes won’t be as dramatic. Dropping weight when you’re already slim is much slower; for me, going from 135 to 128 took months of plateaus and fluctuations. You have to look at the long-term trend over several months. I went down two dress sizes even though the scale didn’t move much. Three weeks isn’t really enough time to see a huge difference, especially with female water retention. I stayed on OMAD the whole time and eventually saw results.