It has to do with your hormones leptin and ghrelin. Your levels get all sort of messed up and it leads to them telling your body you're hungry when you're really just tired. And to top it off, when you're sleepy, you load up on sugar, grab take out for dinner because you're tired, and skip the gym for the same reason. That's three strikes right there.
Some antidepressant medications can cause weight gain, especially the older tricyclic antidepressants (TCAs) such as Tryptizol, Saroten, and Clomipramine; as well as newer drugs such as Remeron (Mirtazapine). Lithium (for manic-depressive disorder) often causes weight gain. The most common antidepressants known as SSRI’s (for example Citalopram and Sertraline) usually don’t impact weight significantly. More on depression
"When we’re lacking in sleep, our body’s hormones get thrown off balance which can impact our hunger levels the next day. We all have two hormones that affect our appetite: ghrelin and leptin. When we don’t get enough sleep, our ghrelin levels (the hormone that makes us feel hungry) rise, and our leptin levels (the hormone that makes us feel full) drop. This means that when we’re awake, we tend to eat more but feel less satisfied. Try going to bed a little earlier than usual to avoid this imbalance and remember to remove any distractions that might prevent you from nodding off."
This drug is an injected variant of a satiety hormone called GLP-1. It slows down how quickly the stomach empties and tells the brain that you don’t need to eat yet – a great idea for losing weight. As a bonus this drug works fine while one is on the keto diet and it works even better with intermittent fasting – for a rapid weight loss with no hunger.
Avoid Junk Food – While you are at it, make sure that you do not eat junk food by any chance. By eating junk food, you are creating your chances of getting slim, very slim. Junk food like fries and burgers and flavored sodas are the worst enemy when you are aiming to lose weight. Instead of snacking on these, you must eat nuts, and fruits when feeling hungry. https://www.youtube.com/watch?v=TyXnVTALGM0