Eating of fatty foods is one of causes of gaining weight. There are many things that are responsible for gaining weight.
If you have family history of obesity, you might gain weight suddenly. So, gaining weight is also related to your family history.
Medicines has side effects. When you take medicines, you can gain weight as a side effect of taking medicines.
Depression and stress
If you are under depression and stress, that could be the cause of gaining weight. Stress can be from your professional life or personal life. It leads to emotional eating.
Large portion of food
You are eating healthy, but still gaining weight. If you eat a lot, it could be the reason of gaining weight.
When women are pregnant, they have to eat more. They usually gain weight at that time.
Scientists found that if you sleep less, this can cause weight gain. So, sleep deprivation is one of the reasons.
If you do not move much, sit and watch TV or play video games for example, you can gain weight. You have to change your lifestyle to lose weight.
Still there are many cause of gaining weight. I just mentioned some of the causes above.
The human body cannot store fat without the presence of insulin in the blood. Insulin tells the fat cells to load up on fat. Insulin secretion is triggered by elevated blood sugar. In fact, you can get fat by following a low fat diet as long as you have enough calories in it. Even a very fatty diet without enough carbohydrates to keep your blood sugar high is unable to fatten you. That's what Atkins' diet is based on: avoiding carbohydrates.
Of course, if you eat a lot of fat it may upset your stomach or cause gall stones or something else. If you want to lose weight, reducing high-quality fats is totally unnecessary. What you should do is cut down on high-glycemic index carbohydrates (white flour, added sugar etc.) in your diet. If you eat enough carbs to have a balanced diet but not too much and mostly low-glycemic index ones (=not capable of being released into the bloodstream too fast), then you will most likely be able to keep your weight in check unless you get too many calories.
NO! The majority of the new research now suggests that fatty foods dont make us fat, and that sugar is a major contributor. The old adage was that fat made us fat, and so to make things taste good manufacturers just pilled in the sugar (this was around the 1970s), and over time people started getting obese, even though they were eating low fat foods.
Now there are essentially 'high fat, low carb' diets which people lose weight. Some are eating as high as 70 or more % fat! Part of it comes down to the tyoe of fats they are eating - animal fats, and other healthy fats, such as avocado, nuts and seed. These diets are also low carbs and pretty much zero sugar.
So sugar is probably the number one reason for weight gain. Obviously it comes down to genetics and age aswell, Younger people with 'skinny genes' seem to stuggle to put on weight while others have more of a tendency to gain weight easily.