In a recent article in the American Journal of Clinical Nutrition it discussed whey protein and how it inhibits Carnitine accumulation. Formed from amino acids Lysine and Methionine, Carnitine’s role is transporting fatty acids to the Mitochondria. By helping breakdown long chain fatty acids Carnitine promotes oxygen consumption.
The Mitochondria are what provide the body's energy needs. Due to its insulin dependency Carnitine is poorly absorbed into muscle cells. A study by Nottingham university found that muscle carnitine absorption increased following a high carb meal, however it was decreased following the intake of whey protein.
Conclusion, if using Carnitine for fat loss, its needs the presence of Carbohydrates, If your body fat levels are low then this will be useful for pre contest athletes however if you're carrying a larger degree of body fat then it will do very little for your fat loss as the higher carbs required will increase your insulin sensitivity which would make taking Carnitine pointless.
Read more- Shannon C E et al, Protein ingestion acutely inhibits insulin-stimulated muscle carnitine uptake in healthy young men American Journal of Clinical Nutrition, 103:276-282, 2016