Its not unfair, its fact. It has been biologically proven, that in some people, the GLP1 hormone receptors are less responsive than in others. GLP1 does a number of things, but simplistically, it signals our brain when we are full and to stop thinking about food, when the receptors stop receiving the message, we are hungry, and start thinking about food. In many overweight people, the physical feeling of full occurs, but the message to stop thinking about food doesnt. Its overwhelming, loud, there or the time, or its a background whisper constantly gnawing away. Its not just sweets and cakes that make people obese, its all foods, or sometimes not even foods at all, in my case it was drinks. In people whos receptors work well, they may be able to resist having that second helping of dessert, a chocolate bar when they pop to the shop, or a pastry on their morning commute, or a daily frappucino, because it isnt a constant noise in their head. Being able to actively chose not to do something is much easier when its occasional, not constant. Its the same battle, yes, but the frequency is different. This difference in how receptors respond is medically proven, and why MJ works for emotional, reactive eating. Because when those feelings are overwhelming, the noise saying have food is no longer there, so you find other coping mechanisms. A lot of people on MJ are taking up more exercise too, because they have the clarity to be able to make that decision without this noise shouting "food" at them all the time, or more mindfullness type hobbies etc.
Yes it works with insulin as well, but this response to GLP1 and making receptors hypersenstive, instead of barely reacting, is why it is also licensed for weightloss alone and not just for diabetics, because it "fixes" a genetic, biological difference in people, one that directly causes obesity.