if your just running and cycling, taking protein will probably have no effect. Most people take protein before/after doing weights, this is because the muscles need protein to repair and build up, and can actually use far more protein than you can realistically get from a normal diet. So if you take protein you know your muscles will rebuild as much as they can, whereas if u dont a lack of protein may slow the build up of muscle tissue.
For aerobic exercise i dont believe there are any specific reasons to take protein, your normal diet should be sufficient. If anything have a snack or energy drink within 30mins off finishing as this replenshes your muscle glycogen stores quickest, meaning you should feel less tired, or something like that anyway. it should also help get rid of fat as you should be less likely to keep on snacking.
If you seriously want to lose a fair amount of fat, try sucking on a lollipop after sessions rather than eating, it gets your blood sugar up again so you dont feel so tired or hungry but they have next to no calories.