Three weeks into fasting. The scale melted the first week, then settled. You add creatine and, a few days later, it climbs back up. First reflex: "I'm gaining fat back."
No. You're gaining water. And it probably went exactly where you want it.
What your scale actually measures
Your scale adds up everything: fat, muscle, bone, whatever is sitting in your gut, and a lot of water. Fat moves slowly. Water can swing from one day to the next. When the number jumps within a few days, it's almost always water talking. Especially when you eat inside a tight window.
Why the scale dropped so fast at the start
Your muscles and liver keep a reserve of glucose stored as glycogen. That glycogen is stored with water. The classic reference (Olsson and Saltin, 1970) puts it at 3 to 4 g of water for every gram of glycogen. A 2023 review in Nutrients points out that the exact ratio is still debated, but the principle holds: when glycogen drops, some water leaves with it.
Add the sodium your kidneys dump early in a fast (we covered it in the dizziness article), and a good chunk of that first "loss" was water. That's fine. It just wasn't all fat either.
What creatine does
Creatine pulls water inside the muscle cell. It's osmosis: more creatine in the cell, more water follows it in.
In 1996, Hultman's team gave men 20 g of creatine a day for 6 days. Their muscle creatine rose by about 20%. In the first days, their urine volume dropped by roughly 0.6 liters: the body was holding on to water instead of clearing it. The researchers saw this as an explanation for the weight gain reported in other studies.
The same work shows the other route: at 3 g a day, muscles reach the same ~20% increase, but over 28 days. Same destination, gentler climb.
So what you see on the scale is two water shifts stacked on top of each other: some of the water you lost early in your fast, plus the water creatine draws into your muscles.
Water retention or "bloat"? Not the same thing
When people say "water retention," they picture a puffy face and swollen ankles. That's water outside the cells. Creatine works mostly inside the muscle cell.
A 2021 review in the Journal of the International Society of Sports Nutrition (Antonio and colleagues) sums up the research: in the short term, creatine increases water mainly inside the cells. Over longer periods, several studies show no change in total body water relative to muscle mass. Their conclusion: creatine may not lead to water retention in the way people usually mean it.
A well-hydrated muscle cell isn't a flaw to fix. It's a muscle working in good conditions.
How to read your scale without losing your mind
- Watch the trend, not the morning number. Compare averages over three or four weeks.
- Weigh in under the same conditions. Same time, fasted, after the bathroom.
- Grab a tape measure. The water creatine pulls in goes to muscle first. If your waist keeps shrinking, so is your fat.
- If the jump stresses you out, skip the loading phase. 3 to 5 g a day gets you to the same level in about four weeks, with a more gradual climb on the scale.
- Don't cut water to "de-bloat." Keep your hydration and your electrolytes. Dehydrating yourself to move a number is playing against yourself.
What we don't know yet
As far as we know, no study has tracked the weight curve of people starting creatine in the middle of intermittent fasting. What we're giving you here combines two separate bodies of research: glycogen and water, and creatine. It's a logical inference, not a direct trial of this protocol. And the size of the jump varies from person to person.
Bottom line
If the scale jumps right after you add creatine, change nothing for two weeks. Measure your waist, track your strength in the gym, and judge over time. Fat doesn't come back in four days. Water does. And it's the right water.
We're building Lyte & Loaded (electrolytes + creatine, zero sugar) for people who fast seriously and want to understand what's happening in their body, not just a number on a scale. Join the waitlist to hear when it launches. Feed the mission. Not the hunger.
This article is for information only and does not replace advice from a health professional. If you have a kidney condition or take medication, talk to your doctor before starting creatine.
Sources: Hultman E et al., "Muscle creatine loading in men," Journal of Applied Physiology, 1996; Antonio J et al., "Common questions and misconceptions about creatine supplementation: what does the scientific evidence really show?", Journal of the International Society of Sports Nutrition, 2021; Olsson KE, Saltin B, "Variation in total body water with muscle glycogen changes in man," Acta Physiologica Scandinavica, 1970; "Muscle Glycogen Assessment and Relationship with Body Hydration Status: A Narrative Review," Nutrients, 2023.
French version: Pourquoi la balance monte quand tu ajoutes de la créatine
Also read, the fasting and electrolytes series: Why You're Cramping Mid-Fast · More Water While Fasted Isn't Always Safer · Why You Get Dizzy Standing Up Mid-Fast · Why Your Heart Pounds Mid-Fast · Why You Twitch and Sleep Like Garbage Mid-Fast · Why You Get a Headache Mid-Fast · Why Your Uric Acid Spikes Mid-Fast · Why You're Always Cold Mid-Fast · Why Your Creatinine Spikes on a Blood Test · Do You Need Sugar to Get Creatine Into Your Muscles?