We have a natural tendency to avoid fats when we are on a diet. And there is a good reason for it, as they are exactly what we are trying to get rid of. However, when we talk about ‘fats’ we are actually referring to a large group of molecules with different biochemical and nutritional properties. And ingesting some types of fats is crucial to keep our bodies healthy.
Fats are also called triglycerides and one of their main features is that they are insoluble in water, which is probably the reason why they evolved into storage molecules: by displacing water, they can be accumulated without the extra weight of the water molecules. They are also quite energetically dense, with every gram of fat producing circa 9 kcal of energy, which is twice what carbs or proteins yield (see “Good Carbs vs Bad Carbs for Weight Loss” and ‘The Importance of Protein’ for more information on carbs and proteins respectively).
Triglycerides are formed by three fatty acids attached to a molecule of glycerol. While the glycerol, molecule has a fixed structure, the fatty acids can be of different types and lengths. You’ve probably heard of saturated and unsaturated fats. These terms refer to the types of fatty acids in the triglyceride molecule, with saturated fats having more hydrogen atoms in their structure than unsaturated fats.
Unsaturated fats are healthier than saturated fats. Two of them, the omega-3 and the omega-6 fatty acids, are “essential” for humans, meaning that our organism absolutely requires them but it is unable to produce them. And the consumption of diets rich in oleic acid, another unsaturated fat, has been linked to a lower incidence of insulin resistance. Common sources of unsaturated fats are fish and vegetable oils, walnuts, almonds, avocado, sardines or salmon (if you like avocado, check out the recipe to ‘Superfood guacamole‘).
However, there is a group of unsaturated fats that should be avoided: the trans fats. Trans fats are rarely found in nature, being instead a byproduct of industrial food processing. They can be found in things like fried fast food or margarine. Their consumption has been linked to a higher risk of coronary heart disease, with a study even showing that for every 2% of calories from trans fat that you eat, the risk of heart disease increases by a staggering 23%. This, together with the fact that trans fats have no known health benefits, has prompted the FDA to determine that by 2018 no processed food should contain trans fats.
And what about saturated fats? Saturated fats sit somewhere in between the unsaturated fats and the trans fats, being neither as healthy as the former nor as pernicious as the latter. They are naturally found in foods like red meat and full-fat dairy products. It is OK to have some, but experts recommend keeping them below 10% of the ingested calories a day.
So remember, next time you feel tempted to speak badly of fats, remember that not all fats are equal, and while some are a no-go others are perfectly healthy. Don’t make the just pay for the sinners!