Is there a way to prevent weight gain after a very low calorie diet?

Yes: Weight gain can be prevented or overcome by a permanent change in lifestyle and in personal outlook. If a person eats fewer calories than he needs to live on each day, his body will use the stored fuel (fat). If a person exercises more than he did before, but does not start eating more calories, then his body will use up the fat (stored fuel). Easier said than done, but definitely possible to do.

Yes 80/20 diet: Where 80% of your diet consists of low carb, high lean protein and plant or fish based fat and no alcohol and 20% is rather unhealthy, meaning higher carb diet. If one can follow that (and I have many patients who are on it for maintenance) for most part, they can maintain their weight. So about 2 meals and 1 snack healthy and 1 meal is considered the "guilty pleasure".