Honestly, IF isn’t some quick fix drug and I think every single person will have different results to it.
I always believe that it takes a minimum of 2 weeks to track any changes and for your body to accept / reject it.
Repeat after me:
“NO SCALES FOR THE FIRST MONTH.
NO SCALES FOR THE FIRST MONTH.”
One week is way too early to see anything except water weight coming off. This is a long distance marathon, not a sprint.
For constipation I drank a lot of water a day, you can google how much you should be drinking. And supplemented with a lot of bran on my meals.
Highly highly recommend listening to the audio book for Fast Feast Repeat! She says to not weigh for the first 28 days! Are you doing a clean fast in terms of only water, plain tea or black coffee during fasting hours? As for the constipation, give that a little time too. Your body is adjusting to the new normal.
A week is nothing, especially for women, who can retain a lot of water depending on where they are in their cycle. As far as constipation goes I recommend eating one celery stick (dip it in hummus) per day to get things moving.
I’m a relative newbie to the world of IF, as well. The first two weeks was probably the toughest for me, but once you get used to everything it’s smooth sailing from there. I didn’t experience any major changes until maybe around the 6 week mark at the latest. I’m in my 3rd month and have lost 17 lbs now.
In all the time I’ve been fasting, I’ve only experienced lightheadedness maybe once or twice. It had to do with the few times my fasting schedule was thrown off. What works for me is starting fast at 8 pm. Assuming that you go to bed around 9 pm and wake up the next day at 7 am, that’s 10 hours of your 16 hour fast. The only thing you have to do is skip breakfast and break your fast at 12 pm (lunchtime). I’ve been doing this fast Mondays through Fridays and it has been working for me so far.
Edit: constipation might have something to do with the food you’re eating. Eating foods rich in fiber might help. Quinoa, bananas, lentils, and greens helped with my digestion.