God made us in all shapes and sizes. Are you being truly honest with you "healthy food" and exercise regime? If you are then, that is the way you are meant to be as earlier said.
The only other things I can think of are:
1) Your water intake. Are you drinking 2 litres a day (more if exercising?) This will increase metabolic rate.
2) Are you working to the correct heart rates. This is so very important in weight management. Fat reduction requires the correct heart beats per minute (bpm) The rate you personally need is about 106-110 bpm which really is not that high. This is taken from the standardised formula 220-43 (your age) and working to 60-70 percent of this figure. Any higher, believe it or not you will NOT be losing fat. Less truly is more.
Buy a heart monitor. The greatest investment for weight management ever.