If your parents have been wealthy you are more likely to have a better overall upbringing. One of the most important factors for what people summarize as intelligence is nutrient supplementation. Poor mothers are in a disadvantage. Traumatic experiences resulting from poverty such as night shifts and economic difficulties can be detrimental to the development of those children.
Food and sex often remains the only gateway for joy for poor people. Their economic power cannot buy them easily anything else and the joy hovers somewhere between specials in Walmart and TV. This in turn results in poorer and less intelligent individuals that have to deal more with health issues rather than trying to escape their fate.
Even more so, dieting, or proper nutrition up-keeping is counter evolutionary. We are designed to search for food and have it on scarcity. Anything that comes along is OK as far as our body can tell. Nutrition being readily available on a daily basis creates the same freak scenario as pet dogs and cats. They don't have the capacity for something more other than fulfilling basic biological functions. A poor person resembles a pet for the rich. They keep the masses happy by feeding them sugar and fat while they receive the cheap labor. The rich on the other hand have the time to plan their meals, go to specialists and evaluate their choices. It is no wonder that BMI can determine status as many studies have shown.
At this point, I am supposed to say that YOU can change your fate if YOU believe in it and all that crap. It might hold true because in reality you are much richer than 75% of the planet. So really you are not in such a dire position as you think you are. With this short essay I am not advocating for socialism, marxism or any similar bullshit like that. I am just stating simple facts of life and how people should make sense of it all. There are basic truths about life, our bodies, and how everything works and really, no motivational book and no religion can change these facts.