Started a diet and exercise at the same time, and suddenly saw that you gained weight instead of losing it? Is it possible that the exercise is causing this?
A participant in my diet course recently started strength training, followed the menu strictly according to the plan, and yet within two weeks discovered a weight gain of about half a kilogram. She asked me something that many people ask quietly: Is it possible that the workouts themselves caused the gain?
The short answer is yes, it is definitely possible.
However, in the first two weeks, the reason is almost never a new half a kilogram of muscle.
Usually, it is a combination of fluids, glycogen energy stores in the muscles, the recovery process from the workout, and sometimes also a slight actual increase in muscle mass. The scale alone, as we will soon see, is simply not smart enough to tell us what exactly changed in the body.
Muscles store more fluid than you think
When starting strength training, muscles are exposed to stress they are not used to. The workout creates minor, normal damage to muscle fibers, and the body responds with a repair and recovery process – a process that involves a temporary accumulation of fluids in the tissue.
At the same time, muscles begin to store more glycogen, the carbohydrate used by them as fuel, and every gram of glycogen is stored in the muscle along with several grams of water.
Thus, an increase in glycogen stores can manifest as weight gain, even without adding a single gram of fat to the body. The phenomenon is particularly prominent in the first few weeks, after a particularly hard workout, or when experiencing muscle soreness. So yes, half a kilogram in such a short period can be mainly fluids, and nothing more.
How much muscle can actually be built in two weeks?
Beginners can add muscle mass faster than veteran trainees, but building muscle is nonetheless a gradual process, not a sprint.
One cannot conclude from a weight gain of half a kilogram within two weeks that this entire amount is pure muscle. Home measurements of fat and muscle percentages are also not always accurate; they are affected by fluid intake, salt, the previous meal, time of measurement, and in women, hormonal changes as well. In studies on resistance training in overweight people, an average addition of about 0.8 kg of lean body mass was found, but that was over training programs lasting whole weeks and months, not a few days.
So does more muscle not burn a lot of calories?
It is true that muscle is a metabolically active tissue, and preserving it is very important during weight loss.
However, the brain, liver, heart, and kidneys also consume a lot of energy, and a small addition of muscle increases resting energy expenditure, but not dramatically. Half a kilogram of muscle alone will not burn hundreds of additional calories a day, nor will it suddenly accelerate weight loss.
So what is the big advantage of strength training, if not a new "calorie engine"?
Workouts help preserve muscles during a diet, improve strength and function, and allow the body to lose more fat and less lean tissue. Even if the overall weight at the end does not drop more compared to diet alone, someone who combines strength training preserves lean mass better and loses more fat.
The scale can stall right when the body is actually changing
Suppose someone lost half a kilogram of fat, and at the same time added a little muscle, glycogen, and fluids. The weight on the scale can simply stay in place, even though the waist circumference decreased and actual body composition improved.
This is precisely why strength training can create frustration for those who focus only on the number on the scale.
A single weigh-in cannot distinguish between fat, muscle, fluids, and digestive tract contents, which is why it is worth tracking waist circumference, how clothing fits, strength during workouts, and progress photos over time.
So when does weight gain from muscle stop? The body does not add muscle indefinitely just because you continue training, but there is also no precise point where it suddenly stops. As the body adapts to training, the same load creates a smaller stimulus, and therefore the rate of muscle building usually slows down over time.
To continue making progress, you can gradually increase weight, repetitions, or execution quality, but even without constantly increasing working weight, you can maintain muscle and improve skill and strength.
Those who do not train for bodybuilding purposes are not expected to continue gaining weight forever. Building significant muscle mass requires time, appropriate training, and yes, sufficient protein and energy.
Sometimes the reason is simply increased eating:
Not every gain after starting workouts is related to muscle or fluids. Physical activity can increase appetite, and sometimes a seemingly justified feeling is created that eating more is allowed because, overall, you worked out. A post-workout snack, sports drink, extra nuts, or just a slightly larger meal can quickly return all the burned calories, and sometimes even more.
Smartwatches and fitness devices also tend to overestimate actual caloric expenditure.
If the weight gain continues for several consecutive weeks, it is worth checking portions, snacks, and small changes that crept in around the workouts.
How long should you wait before drawing conclusions?
Two weeks is too short a period to conclude that exercise is hindering weight loss.
Body weight can fluctuate from day to day by more than half a kilogram, simply due to fluids, salt, carbohydrates, bowel movements, and the time of weigh-in. It is best to weigh yourself under similar conditions each time, and look at the trend over three to four full weeks.
If waist circumference decreases, clothes become looser, and strength improves, it is a sign that the process is moving forward, even if the scale temporarily does not budge. If both weight and circumferences continue to rise over time, it is time to re-evaluate the menu, rather than automatically assuming that it is all muscle.
So the bottom line: Yes, starting strength training can definitely cause temporary weight gain, mainly due to glycogen and fluid retention and the muscle recovery process. There is no reason to panic over a two-week stall or small increase, and certainly no reason to stop working out. Stick to the menu, track circumferences as well, and give the body enough time to show what has truly changed beneath the surface.