Theoretically, you can lose weight by dieting. From a biological point of view, when the human body lacks glucose, it will decompose fat and glycogen, thus achieving the effect of reducing fat. But it should be noted that when the human body consumes a lot of fat to provide energy, it means that your glycogen has been exhausted. At this time, people are extremely weak and your liver is seriously damaged, so dieting can't actually lose weight without damaging your health. I suggest you pay attention to a healthy diet.
Losing weight still needs exercise, but we should pay attention to the method of exercise. Exercise can lose weight and make people strong. Some sports need strength, especially when people are already fat. Because of the need of strength, muscles will thicken until they can provide such great strength, which is why many obese people can't lose weight after exercise. It is suggested to buy a book related to this aspect and choose an appropriate exercise mode.