Alone, neither of them is sufficient.
Some people are able to shed pounds just by cutting calorie intake, but the results are unlikely to last without some physical activity. Conversely, you can spend hours in the gym, but if you’re stuffing your mouth with high-caloric and unhealthy food you won’t go far.
To put it differently, both factors are necessary to achieve optimal weight loss.
Exercising without a healthy diet is futile, but an healthy diet is per se not enough.
However, it’s not always apparent how much these two factors plays in the weight loss equation.
In other words, how much should you exercise? How much you should restrict calories?