Losing weight by weight training

There is "fat weight" and "muscle weight". To lose fat, you simply restrict calories and use a "segregated diet" instead of a "balanced diet". With such a diet, you don't have to train, although you can if you wish. A "segregated diet" means, you eat carbs with fats at one meal, and protein and fats at the next and fruits by themselves. Which implies eating five to seven meals per day, every day. Drink water according to your thirst. This should reduce any stomach bloating you may have.
Muscle weight, or what bodybuilders would call muscle mass, is built by protein, relatively low fats, and some carbohydrates, mostly "fibrous carbs", ie. non-starchy vegetables and legumes, and few fruits, especially right before and right after training with weights. Again, five to seven meals a day are best. Water should be consume very generously, to the rate of at least one cup every waking hour.
In your post, the problem you expose is that you don't eat enough overall calories and grams of protein, and the protein shake you describe is too high in fat because of the peanut butter. You therefore short-circuit your weight training gains.
Better to use 1/4 cup of very good vanilla ice cream, an excellent whey protein, with banana and skim milk, and voila! Before training, you can have oatmeal, small berries and a scrambled egg omelet (maybe one or two whole eggs with 1/2 a cup to a cup of egg whites)...Wait 45 min and train, then, upon returning, have the protein drink I mentioned, then 2 1/2 to 3 hours later, have chicken, or fish, or beef, with fibrous carbs (green vegetables) and some starch (brown rice, sweet potato). Over the course of a day, you should consume at least one gram of protein per pound of the desired bodyweight (0.5 g per kg of bwt) you're aiming for. You should eat as much if not slightly more carb grams per day as you would protein grams. Your fats (in calories), should hover between 20 to 33% of total daily calories eaten each day.
Weight training should be performed, depending upon your level of experience, three to four days a week, 45 to 55 min in duration, and cover the whole body, without "stressing out" over the waist, especially if you are over 40. Remember that as you gain muscle weight, you lose fat! Therefore, your weight might not go down on said scale, but the mirror and the tape measure should quickly show you results!
After you see dramatic change in the mirror from a high-protein, low fat diet, combined to proper weight training, your bodyweight might even go up! Great! As long as the waistline keeps going down! After three to four months of such a regimen, you might want to increase "fun and interesting aerobics", probably outdoors, for at least 45 min a day, three to four days a week, and then, whatever fat and water retention your body might hold on to will melt away, leaving behind nothing but muscle! Time to shop for new clothes and enjoy!
So, to sum up, if weight loss and slimming down is the main focus, use a segregated diet to "un-bloat", where training is not paramount; otherwise, if looking fit and muscular is the goal, combine the use of a high-protein, low-fat bodybuilding diet, to weight training, where how you look in the mirror predominates over how much you weigh on the scale!
I wish you great results!

There is "fat weight" and "muscle weight". To lose fat, you simply restrict calories and use a "segregated diet" instead of a "balanced diet". With such a diet, you don't have to train, although you can if you wish. A "segregated diet" means, you eat carbs with fats at one meal, and protein and fats at the next and fruits by themselves. Which implies eating five to seven meals per day, every day. Drink water according to your thirst. This should reduce any stomach bloating you may have.
Muscle weight, or what bodybuilders would call muscle mass, is built by protein, relatively low fats, and some carbohydrates, mostly "fibrous carbs", ie. non-starchy vegetables and legumes, and few fruits, especially right before and right after training with weights. Again, five to seven meals a day are best. Water should be consume very generously, to the rate of at least one cup every waking hour.
In your post, the problem you expose is that you don't eat enough overall calories and grams of protein, and the protein shake you describe is too high in fat because of the peanut butter. You therefore short-circuit your weight training gains.
Better to use 1/4 cup of very good vanilla ice cream, an excellent whey protein, with banana and skim milk, and voila! Before training, you can have oatmeal, small berries and a scrambled egg omelet (maybe one or two whole eggs with 1/2 a cup to a cup of egg whites)...Wait 45 min and train, then, upon returning, have the protein drink I mentioned, then 2 1/2 to 3 hours later, have chicken, or fish, or beef, with fibrous carbs (green vegetables) and some starch (brown rice, sweet potato). Over the course of a day, you should consume at least one gram of protein per pound of the desired bodyweight (0.5 g per kg of bwt) you're aiming for. You should eat as much if not slightly more carb grams per day as you would protein grams. Your fats (in calories), should hover between 20 to 33% of total daily calories eaten each day.
Weight training should be performed, depending upon your level of experience, three to four days a week, 45 to 55 min in duration, and cover the whole body, without "stressing out" over the waist, especially if you are over 40. Remember that as you gain muscle weight, you lose fat! Therefore, your weight might not go down on said scale, but the mirror and the tape measure should quickly show you results!
After you see dramatic change in the mirror from a high-protein, low fat diet, combined to proper weight training, your bodyweight might even go up! Great! As long as the waistline keeps going down! After three to four months of such a regimen, you might want to increase "fun and interesting aerobics", probably outdoors, for at least 45 min a day, three to four days a week, and then, whatever fat and water retention your body might hold on to will melt away, leaving behind nothing but muscle! Time to shop for new clothes and enjoy!
So, to sum up, if weight loss and slimming down is the main focus, use a segregated diet to "un-bloat", where training is not paramount; otherwise, if looking fit and muscular is the goal, combine the use of a high-protein, low-fat bodybuilding diet, to weight training, where how you look in the mirror predominates over how much you weigh on the scale!
I wish you great results!

:huh: Segregated diet? Eating 7 times a day? Cutting out peanut butter?

No. Just no. OP, don't listen to this.