Intermittent Fasting Muscle Loss?

[Ifnewbie]

I did my first fast 4 days ago for 24 hours.   I've also skipped breakfast 2 days.   I was feeling great and excited to jump on the scale.   I had loss 4.5lbs but also 5lbs of muscle mass.   What did I do wrong?

The scale was an Inbody 270 at my gym (https://inbodyusa.com/products/inbody270/).  It apparently uses Bioelectrical Impedance Analysis to measure body fat and lean muscle mass.

Everything I've read on intermittent fasting said you don't lose muscle through fasting.   I'm exercising with weights and running.  I'm also eating a very clean diet with no processed foods, sugar, or gluten. Any thoughts on what to switch up?

[JohnnyRow]

I expect much of your weight loss was temporary water loss, as the fasting temporarily messed with your body fluids balance.  To bioelectrical impedance measurements, water loss looks like muscle loss.  I would not jump to conclusions for a few days to let you body's fluids get back into balance.  I would expect you will see some of the weight come back, with a corresponding increase in measured muscle mass.

[MarreFitbit]

Hello there @Ifnewbie!

I will go with @JohnnyRow's resolution... I'm doing fasting since last Nov, first weeks your body is going into a change and it needs to be adapted to it.

Are you doing the keto diet? If so, keto diet lose muscle even when they continue resistance training. This may be related to the fact that protein alone is less effective for muscle building than protein and carbohydrates together after exercise. People following the keto diet for three months lost about the same amount of body fat and had about the same muscle mass changes as people following normal diets. Yet the folks on keto did lose more leg muscle. 

In case you're doing this diet and want to build or mantain your muscle, check this article that I found really helpful: Keto Bulk - Can Muscle Building and Low Carbs Work Together?

Let us know how it goes. 

[Dominique]

Body composition just doesn’t change in a few days, or even in a few weeks. What you observed with your gym’s device is merely proof of the limitations of BIA as a technology (regardless of the bold claims InBody makes on their site) for estimating lean mass vs. fat mass.

While nutrition does play a role in body composition, nutrient timing (e.g. fasting once in a while, or skipping breakfast) is not among the key factors. Energy balance (calories) and macronutrients (e.g. protein intake) are far more important.

Therefore I wouldn’t "switch things up" based on the numbers you saw at the gym. If you know you are doing the right things for your goals in terms of exercising and nutrition, just keep doing it. Consistency is what brings results, over time.