Spray a large saucepan with low calorie cooking spray and place on a medium heat.
Add the onions and garlic and fry for 10 minutes, stirring, until golden and softened slightly.
Add the carrots, stock and thyme, cover and simmer over a low heat for 25 minutes until the carrots and onions are tender.
Carefully transfer to a food processor and blitz until smooth. You may need to do this in two batches. Alternatively, use a handheld stick blender.
Transfer the soup back to the saucepan. Stir in the orange juice and season to taste with salt and pepper.
If needed, heat, uncovered over a low heat for 2 -3 minutes until piping hot and serve.