What's the final answer on if Diet Soda breaks the fast?

Well, I knew this was coming. I know I've gained a lot of weight in the past three years. But I just got blood work back, and my a1c is very high. I NEED to lose weight. I feel like shit. I think IF is the best possible chance I have to do so. My biggest problem is my diet coke addiction. I don't drink alcohol; I don't smoke. I don't do drugs. I just drink a lot of diet coke. I am glad I like the taste of aspartame, and I find regular soda too sickly sweet. I wake up in the morning, and I need a diet coke to help me wake up for my first meetings of the day. I know it's been a controversial topic, but what is the final answer on the science if drinking Diet Coke spikes glucose? Is it considered breaking the fast? I'm depressed and scared. And I'm really hoping I can make this work, but I want to be realistic. Thanks for any advice and support.

Answer

There simply is no “final answer.”

It won’t spike glucose. It might spike insulin. Or it might not. The scientific studies show massive person-to-person variability in whether a sweet taste causes an insulin spike. It seems to be one of those things where everybody is different. If it does spike insulin, the spike is likely to be very short-lived. Biological effects of such a short-lived insulin spike are not known. It probably won’t affect weight loss much, but I’m not aware of any data about whether/how it affects insulin resistance.

All of that said — you can absolutely get started doing IF while still drinking Diet Coke. Don’t let it hold you back, and don’t let the perfect be the enemy of the good. You can start where you are, even with drinking Diet Coke every morning, and still get plenty of benefits from fasting.

I mean, when I started IF, I still put cream in my morning coffee for the first several months. That was a “dirty fast” and it for sure caused a temporary rise in insulin. I still lost weight and it was still 100% worth doing IF, even though it was “imperfect.” I’m really glad I didn’t give up on IF just because I wasn’t ready to give up cream in my coffee.

My bigger concern about drinking a ton of Diet Coke every day is the effects on your teeth (even sugar-free soda is very acidic, which will wear away your tooth enamel) and the effects on your kidneys — drinking 2+ diet sodas every day has been linked to a substantial decrease in kidney function over the long term. For those reasons, I’d encourage you to think about cutting back. But those are separate issues from IF and weight loss.

You may even find that as you get used to fasting, it’s easier for you to cut back on the Diet Coke. Fasting can change a lot of things about how you feel. I think it’s worth a try.

Answer

If you’re fasting for weight loss, this shouldn’t impact that. If you are fasting for any of the other reasons, like autophagy, this breaks the fast.

The fact that you’ve classed soda as a need though is a little concerning. Any sort of chemical dependancy to wake up and function is not great. Have you talked to a doctor about that?