Without knowing your gender, starting weight and goal weight, it's hard to know if this is reasonable or not. However, there are a couple warning flags that I see here. You want to preserve muscle, and possibly build more if that's OK.
Looking at the proposed diet, you have roughly:
- 1550 Calories/day
- 219g Protein/day
- 77g Carbs/day
- 41g Fat/day
If you are a woman, that might be reasonable. However, when I see that coupled with 1000 Cal/day exercise during the week that might not be enough even for a woman. If you are a man, it's entirely too much of a deficit.
You may want to consider carb and calorie cycling. Essentially, what that means is you have a higher amount of carbs on training days, and a lower amount of carbs on rest days. Similarly you do the same with Calories. This helps rebuild the glycogen reserves your muscles need and aids recovery so you can do it all again.
I'm not sure what "gym training" involves, but it appears that your training regimen is at odds with your stated goals. Just repeating your goals:
- gain muscle, not fat
- lose the belly
- Enjoy food on the weekends
The thing is you have a lot of steady state cardio work. That helps build endurance, but not muscle. If "gym training" is using the machines, doing body weight exercise, or even lifting weights, the two activities are fighting each other. Your body will do its best to make a reasonable compromise, but endurance doesn't build muscle. It burns fat, but doesn't improve your muscle mass.
If you want to improve muscle, you need to focus on activities that force your muscles to work. And then keep increasing the effort your muscles have to exert so they do get stronger. The only thing in your conditioning you listed that doesn't conflict with that is boxing. You would do better with Tabata training than cycling.
I lift free weights, and routinely spend at least 1000 Calories per session doing it. The key is to go heavy and improve on that. However, to go heavy you need rest days so you can recover. Your current routine is 5 straight days of work with no rest. That's not good because it will cause you to have elevated levels of Cortisone. That in turn burns muscle, and since you aren't giving your muscles a chance to fully recover and rebuild you will be burning more muscle than you build. Muscles increase during rest, after you put them through heavy work. I would reduce your training days so that you have no more than 2 days in a row. I would also look at more efficient use of conditioning.
Summary and Recommendations
The long story made short is that it looks like you are eating too few calories and exercising too much. This is a recipe for losing muscle. That combined with elevated Cortisone levels will keep more fat around your belly that you are trying to get rid of. Even if you do an epic refeed over the weekend, the combination is likely to force you to overcompensate.
- Be more moderate with your exercise. At least 3 times a week, but no more than 4. Focus on resistance training and High Intensity Interval Training for conditioning. That will help build muscles and improve conditioning in a way that helps resistance training.
- Learn the importance of rest. Muscles cannot grow when they are constantly torn down. A good training session will elevate Testosterone levels and associated growth hormones naturally. Rest allows them to do their job.
- Try a different tact with your diet. The basic principles are there, but it needs some fine tuning.
You might want to experiment with intermittent fasting. If you fast one day a week (a rest day), then you'll set up your diet so that on any given day you are at a 500 Calorie deficit. The day before the fast, you double up the food. You are eating two day's worth of food in one day, and nothing on the next day (aside from green tea and vitamin supplements). This allows you to have a free day a week and still lose weight.
Alternatively you can increase calories and carbs on training days (carbs should be at about 1g/pound body weight on training days), and reduce on rest days. At the end of the week you should have a calorie deficit. 20% up on training days and 20% down on rest days. If you need to adjust the amount of protein you have to make that work, do it. However, there are no free days with this approach.