The question is always: Should I start my workout with strength or cardio?
The answer: It’s best to start with the weights.
If you are working on lightening up and slimming down, weights before cardio works best.
So here is why: If you start your workout with weights, then by the time you go for a run or a bike your anaerobic energy systems will already be worked and spent, meaning your body will have to resort to burning fat to keep your aerobic system going strong, What’ happens here is that you will burn more calories, not just in the gym or on your run or bike, but after your cool-down, too. So more calories burned post workout while you go about your day is the way to go for optimizing your results.