Weight loss happens in your kitchen, not in the gym. Gym is where you build muscle and tone your body. Yes, it's easier to lose weight if you also work out and have more muscle mass. But you simply can't out-exercise a bad diet. Thread let's give an example: Coca-cola. 500ml (16oz) bottle contains roughly 200 calories, all from high-fructose corn syrup. HFCS spikes your blood glucose so high, that you body got no other option but to secrete a ton of insulin and convert all of that directly into fat.