If you're a "little" overweight switching from butter to olive oil, calorie for calorie, isn't going to make a more than negligible difference. In the amount required for bread spread or even dipping, the difference is less than a few dozen calories difference between monounsaturated and saturated fat.
If you're switching because of a taste preference, though, then by all means go for it.
1) eat real food - more vegetables, moderate meat, moderate fruits, less grains, less sugar, less vegetable oils.
2) exercise - moderate intensity cardio, sprinting, heavy lifting, dedicated stretching and mobility.
3) live - relax, de-stress, meditate.
Disclaimer: I'm not professionally qualified to make any formal recommendations. I've just done my homework and I'm my own guinea pig. All of my data, unless otherwise cited, comes from a sample size of n=1 (me).