Both – but with a careful eye on the diet as the first priority…
I tried to do it through the “exercise more” approach for years. Weight steadily climbed from circa 14-14.5 st, up to 15.75 st.
The more I rode, the more I put on weight – a combination of bigger appetite to sustain exercise and bigger frame from combination of calorie intake and increased exrercise.
Taken a markedly different approach this year. Have combined cycling (actually less, but better targeted – mtb and some road) with gym (cardio and strength).
BUT crucially, have also taken a detailed look at my diet. I don’t feel that I have been “on a diet” – just cut back on some of the crap, and tried to getter a better balance between sugar / complex carbs, protein and fat. I try to maintain fat to about 25-30% (although some weeks it is higher…) 50-60% carb and 15-20% protein.
Has worked a treat. Turn of the year I was at 15st 8lbs. By Mountain Mayhem I was 14st 4lbs, and now down the 13st 4lbs.
That’s probably the lightest I have been since I was about 19-20 (and at 45 that feels cheekily good 😛 ). Much fitter on the climbs now, but not sure there’s room for much more weight loss.