You have a friend who lost 7 kg (about 15 pounds of fat on a regimen of strict diet and exercise. how did the fat leave his body? you

Fat let your friend`s body in the form of carbon dioxide and water. Or CO2 and H2O

Explanation:

First of all, let's clarify something. Fat is nothing more than stored energy in the body to be used when needed. So, if your friend started a diet exercise regime that means he reduced his calory consumption which is the source of energy and he increased his energy consumption. Thus, the usage of energy stored in fat cells was activated. The energy made the cells shrink and create heat to keep the movement. That is why the fat/energy was expelled from his body in the means o water and carbon dioxide. Because these two elements are the ones involved in the heat, energy, exercise cycle.