Carnitine supplementation promotes fat loss | Meta-study
You should not exaggerate the weight loss effect of carnitine, but according to a meta-study that appeared in Clinical Nutrition Espen, the stuff does promote fat loss.
Meta-study
Nasir Talenezhad, of Shahid Sadoughi University of Medical Sciences in Iran, collected and re-analyzed 37 previously published trials in which subjects had been given L-carnitine and in which researchers determined the effect of the supplement on body composition. The duration of the supplementation varied from 3-8 weeks, the daily dose of 250-4000 milligrams per day.
A total of 2,292 subjects participated in the studies.
Results
L-carnitine supplementation did indeed effect weight loss. On average, the participants lost 1.2 kg of their body weight and 2.1 kg of their fat mass when they took carnitine. The effect was statistically significant.

As far as Talenezhad could determine, the slimming effect of carnitine was optimal at a dose of 2000 milligrams per day. You can see this above.
The slimming effect of L-carnitine supplementation was greater in studies in which the subjects were overweight or even downright obese.
Source:
Clin Nutr Espen. 2020 Jun;37:9-23.
You should not exaggerate the weight loss effect of carnitine, but according to a meta-study that appeared in Clinical Nutrition Espen, the stuff does promote fat loss.
Meta-study
Nasir Talenezhad, of Shahid Sadoughi University of Medical Sciences in Iran, collected and re-analyzed 37 previously published trials in which subjects had been given L-carnitine and in which researchers determined the effect of the supplement on body composition. The duration of the supplementation varied from 3-8 weeks, the daily dose of 250-4000 milligrams per day.
A total of 2,292 subjects participated in the studies.
Results
L-carnitine supplementation did indeed effect weight loss. On average, the participants lost 1.2 kg of their body weight and 2.1 kg of their fat mass when they took carnitine. The effect was statistically significant.

As far as Talenezhad could determine, the slimming effect of carnitine was optimal at a dose of 2000 milligrams per day. You can see this above.
The slimming effect of L-carnitine supplementation was greater in studies in which the subjects were overweight or even downright obese.
Source:
Clin Nutr Espen. 2020 Jun;37:9-23.