In general, your body tries to be as efficient as possible. The "metabolic boosters" block the normal pathways the body uses to try force the body to use a less efficient (and thus more calorie-consuming) means of completing a normal body process. Because the normal pathway is typically the most efficient one, there is little room to force the body to do things more efficiently (and thus less calorie-consuming) so that more of what you eat "sticks".
That being said - periodic consumption of alcohol forces the body to store more of its calories, but they are stored almost exclusively as fat so that the body has more..... sponge, if you will, to soak up the alcohol.
You can also play games with the thyroid to slow the metabolism but these come with consequences that may not be worth the risk. You can take meds for hyperthyroidism (radioactive iodine, methimazole / tapazole, or propylthiouracil / propyl-thyracul) and you will gain weight quick. However, you'll probably also feel very fatigued, weak, cold - your muscles will cramp, you could feel depressed, irritable and lose your libido. In general I'd say you should stick to controlling it with diet but if you are really concerned that your not gaining maybe get your thyroid checked - you could legitimately have hyperthyroidism.
