I want to know if it is bad or dangerous to consume 2.5 grs of l-arginine before training and another 2.5 grs before bed. i want to lose fat.

Generally safe: 2.5 grams of L-arginine twice a day is within safe limits based on available research. The best way to lose fat is to eat healthy foods (including plenty of vegetables, fruits, whole grains, and legumes), exercise moderately (too vigorously, and you may get too hungry according to recent studies), and take care of your emotional health ("what's eating you" could be why you don't always eat right).

No it isn't.: The only way to lose fat is to take in less calories than you use in a day Exercise won't matter in weight loss if you eat too many calories. Know your calories. Cut 100 calories a day and you will lose about a 1 lb a week (generally speaking) at the same level of activity (calories burned a day). Walking or running one mile a day only burns about 100 cal.