Each gram of fat provides 9 kcal of energy. Fats are essential for the human body as these make up the important part of all tissues and cells. The cell membrane is rich in lipids and brain is full of fat. In combination with proteins and phosphates, fats (lipids) for many important molecules. Linoleic and a-linolenic acids are essential fatty acids.
Trans fats are usually of animal origin or provided by hydrogenation of oils. These are harmful for the body. Poly-unsaturated fats and Mono-unsaturated fats are associated with less risk to heart and brain compared to saturated fats.
Fats of animal origin are more harmful compared to fats from vegetable sources.
In terms of health benefits, olive oil, soya oil, sunflower and safflower oils rank high.
In the body, lipids are measured in blood by the test of lipid profile (best done after 8-10 hrs of fasting). It measures S cholesterol (HDL or high density, LDL or low density and VLDL and IDL very low and intermediate respectively), Triglycerides and few other types of lipids.
HDL cholesterols are thought to be protective from cardiac and cerebrovascular attacks. LDL cholesterol, on the other hand, increases the risk of heart and cerebrovascular diseases.
Fats should usually make up about 30 % of the total caloric intake. About 1 gm/kg/day should be a rough estimate for those who are non-obese. Surprisingly, extra carbohydrates when taken in diet lead to more obesity.
The relation of fats in the diet and risk of cardiac and cerebrovascular disease is not very strong. Similarly, the risk of fats to cancer is also not well proven. However high lipids in blood are related to these disorders.
If Cholesterol, esp LDL cholesterols and triglycerides are elevated, these need to be reduced. Their value may be more in treating patients who are suffering from Ischemic heart or cerebrovascular disorders rather than preventing primary prevention.