I am a 15 year old male, standing at a tiny 5 foot 6 inches and weigh in at 8 stone and 1.1 pound, my fat index is only 10.7% and from my research this suggests that I should go on a lean or "shredding" fitness plan. The problem is I only go to the gym once a week due to school and training. Is this a dieting problem or Can I do more in the gym? It could also be useful to note that I usually stay away from the freeweights section as it is usually packed! Can anyone recommend a fitness plan or even an app on android that could help me out? Cheers
If I've converted units correctly, then "8 stone and 1.1 pound" is 113.1 pounds. At 5 foot 6 inches -- which is not "tiny", in my opinion -- you are grossly underweight. As @xCodeZone commented, "you don't need to cut down your calories"; on the contrary, please consider eating enough food to increase your total bodyweight to, say, at least 170 pounds. Note that you cannot exclusively gain (or lose) muscle or fat: while gaining muscle, you'll gain some fat, and while losing fat, you'll lose some muscle.
In addition to eating more, I suggest heavy squats, deadlifts, and presses for your one day per week in the gym. This will spur muscle protein synthesis, so you'll gain strength and muscular bodyweight (again, in addition to some fat, which you can lose after getting stronger and bigger).