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Instalab ResearchCreatine is a compound your body already makes in small amounts, primarily in the liver and kidneys. It’s stored mostly in skeletal muscle, where it plays a key role in the production of adenosine triphosphate (ATP), the fuel your muscles use for short, explosive movements such as sprinting or lifting weights.
When you take creatine as a supplement, you increase the amount your muscles can store, which allows your body to regenerate energy more quickly during intense exercise. In practice, that means you can push harder, lift heavier, and recover faster. Over time, that extra effort can translate into more lean muscle growth.
In the first week of supplementation, it is common to see a jump in body weight. Clinical studies consistently show an increase of roughly one to two kilograms during the loading phase, which typically involves taking about 20 grams of creatine per day for five to seven days.
This initial gain is almost entirely water. Creatine pulls water into muscle cells, a process known as intracellular water retention. Rather than causing bloating under the skin, this water lives inside your muscles, making them feel fuller and slightly more voluminous.
Physiologically, that is a good thing. The increased hydration may improve muscle function and protect cells from damage during training. It is not body fat, and it does not represent unhealthy weight gain.
After the initial week, the effects of creatine shift. The extra water in muscle cells supports an environment that promotes protein synthesis, the process that builds muscle fibers. As you train with greater strength and endurance, your muscles respond by growing. Over time, this leads to measurable increases in fat-free mass.
Researchers have repeatedly confirmed this pattern. Meta-analyses combining data from more than a hundred studies show that people who supplement with creatine while resistance training gain about one kilogram of additional lean tissue compared to placebo. These gains are not accompanied by increases in fat mass. In some cases, body fat percentage even drops slightly as the proportion of muscle in the body increases.
What this means is that the weight gain from creatine eventually becomes structural. It represents tissue growth, not simply stored water. For athletes, this can be a clear advantage, since the rise in total body weight signals a stronger and more efficient body.
Not everyone responds the same.
While most people see some degree of weight increase, the exact response depends on factors such as diet, muscle fiber composition, and baseline creatine levels. Those who already eat a high-protein, meat-heavy diet may see smaller changes because their muscles are already close to saturation. Vegetarians, on the other hand, tend to experience larger effects since their natural creatine stores start lower.
There is also variation by sex. Some studies suggest that women experience slightly greater short-term gains in lean mass after creatine loading, possibly because of differences in muscle water distribution. However, these differences tend to even out once everyone begins consistent resistance training.
The idea that creatine makes you “gain fat” is one of the most persistent myths in sports science. The confusion arises because the scale moves upward, and most people equate scale movement with fat storage. In reality, the increase represents water and muscle, both of which contribute positively to physical performance and appearance.
In fact, creatine may help reduce body fat indirectly. Because it allows you to train harder and recover more efficiently, you can build more muscle. Since muscle tissue increases metabolic rate, you burn more calories at rest, which can lead to a leaner body composition despite the higher number on the scale.
In most cases, the small increase in body mass from creatine is beneficial. However, for athletes in weight-class or endurance sports, even an extra kilogram can affect performance. In these situations, creatine may need to be used strategically during off-seasons or training blocks where minor weight fluctuations are acceptable.
For the general population, though, there are no real drawbacks. The added muscle volume, improved training capacity, and enhanced recovery make creatine one of the most effective and safest supplements available.
