Seed oils are a huge, more subtle culprit for contributing to weight gain.
The following are some things I have learned from a variety of holistic healthcare practitioners.
Most of these seed oils are processed unnaturally at very high temperatures, and contain chemicals to mask the rancid odour. These fats are very delicate in their original form and are high in omega 6 (can cause inflammation in high amounts), and hence become unstable due to the high heat, causing inflammation and cortisol to increase in the body. In other words, they are toxic to the mitochondria, the powerhouse of the cell.
They contain calories but no nutrition, and so the body is left sending hunger signals which causes our biology to believe we are starving (which in reality is happening with empty calories), and contributes to fat storage around vital organs (for quick energy in emergencies), which is in the stomach area. This is why we see so many people with that large belly, skinny legs look. The fat that people struggle to lose today is frequently in the abdomen.
Seed oils are used everywhere, even in frying steaks at a restaurant. One may believe ordering a steak is a healthy choice, please request that it be cooked in butter instead. Restaurants almost invariably use seed oils for cooking everything. These oils are also in a lot of innocent looking foods, like roasted nuts, organic seed crackers, roasted seaweed, and things of a similar nature. Please read labels!!!
McDonalds actually used to fry their potato fries in beef tallow. Interestingly, people were thinner when that was the case. Now it is done with seed oils, the same batch of oil used repeatedly oftentimes. Hello rancidity and inflammation par excellence!
These oils I am referring to are canola, soy, corn, safflower, sunflower, cottonseed, and more. Seed oils in the past were used as machine lubricant. Then, in order to make more money, there was a propaganda campaign to convince people that lard, butter and tallow was unhealthy, and that "vegetable" oils were. These oils are much cheaper to produce than animal fats.
Healthy fats contain fat soluble vitamins which contribute to mental stability, nervous system regulation, immune system health, and feeling full. Butter, ghee, beef tallow, and lard actually contribute to weight loss and are safe to use at high temperatures, and contain vitamins A, D, E and K, which are also very important for hormone balance and fertility. People were not afraid of fat once upon a time, and were universally slimmer. Lard was even used in baking.
So although there are many things that people are at fault for in relation to being fat, I do understand that ignorance of the dangers of seed oils can also be a factor and more difficult to discern, on account of it appearing healthy since they are often called "vegetable oils" and have "heart healthy" labels on them.
There is also the idea that if we do not eat 3 meals a day, we are doing something wrong, and for children many snacks must be included apart from those 3 meals. This is false and probably came about from the post World War II era, when people were understandably afraid of starving again. Historically, children were completely fine and healthy with 3 meals a day and no snacks. Another reason people snack all the time now, is because their food does not have enough healthy fat in it, with too many carbohydrates.
Those people who crave ice cream at night? This is often due to not enough healthy fats during the day.
For instance, a breakfast may be skim or low fat milk with cereal and orange juice. This will spike one's blood sugar, causing a massive increase of insulin lowering the blood sugar to deal with the spike, and thus they will need a snack only a few hours later.
Some people have such slow metabolisms however, that one meal a day is quite enough for their macro and micronutrient needs. Also, as people age, they may eat the same amount as when they were young and expect to still be slim which is another error, since the nutritional needs of one who is older is not the same, and the metabolism becomes slower over time.
There have been many people, particularly women, who have lost weight by increasing their intake of healthy fats. This is because in a woman's case it is often due to hormone imbalance and high cortisol. The fat contains cholesterol which is the building block of all hormones. So it is also about properly understanding the cause of one's weight gain. I remember hearing of one who did everything right, eating properly and exercising, and her sleep was terrible. Once her sleep was fixed, she lost weight, changing nothing else.
I do not believe in the "I am fat because of genetics" theory. Blaming things on genes seems to be a way in which doctors explain things when they really do not understand the issue. We do not say that some lions are fat, some zebras are fat, eagles and other birds are sometimes just fat because of their "genes", etc. If they are, it is because they are not in their natural environment like in a zoo. Additionally, if there is a deformed animal in the wild, it is quite a rare occurance.
There is a general standard for how the human body should look if it has developed properly and has enough nutrients, with some variations depending on one's race such as height, bone mass (which contributes to muscle capacity), etc.