For many years unsaturated fats have been hailed as the healthiest fats that we could consume. But, in the past few years changes have been made to the way we perceive saturated fat.
In the USA, the FDA removed the maximum recommended daily allowance to make the intake recommendations unlimited after studies showed that it was in fact hydrogenated fats (or trans fats) that were causing health issues. Hydrogenated fats are processed fats that are heated and distorted to create a stable shelf life and are usually found in fast food and processed packaged food. These fats cause massive amounts of inflammation and are now known to be a major contributing factor in metabolic syndrome.
As we are starting to see, saturated fats have been wrongly vilified but most people still consider vegetable fats such as olive oil and rapeseed oil as healthier options over fat from animal products such as lard, tallow, suet, and pork skin. However, research done in 2017 has highlighted some interesting developments in our knowledge.[i]
Vegetable fats are known as polyunsaturated fatty acids (PUFA). Vegetable and seed oils are made up of a substance called 'linoleic acid’; meat-based oils are made up of a substance called ‘stearic acid’.
In this study mice were given a high fat diet above the correct calorific requirement, so weight gain was expected.
The mice who were given linoleic acid had a significantly increased amount of weight gain, insulin resistance and reduced activity compared to the mice who were given stearic acid in the form of tallow. The mice fed on tallow gained the least weight suggesting that it was metabolised more effectively. The researchers went so far as to say that they believed linoleic acid could be a contributor to the obesity epidemic.
Many doctors who have peer reviewed this work (including Dr Paul Saladino) posit that this is because our palaeolithic ancestors would have only eaten nuts and vegetation in times of scarcity (or, in the case of nuts, when winter is coming). The linoleic acid signals to our fat cells (adipose tissue) to go into fat STORAGE mode. Conversely, stearic acid was only present if we’d had a successful hunt and therefore sent the signal to the fat cells that we are in abundance and can safely be in fat BURN mode.
Though the use of olive oil, rapeseed oils and vegetable oils is widespread, all these oils require processing, which our ancestors would not have been able to do. This indicates such oils might not be ‘species appropriate’, plus the fact that the amount they appear in our diets is certainly a newer phenomenon due to reduced costs, increased availability and the fact that meat fats such as ‘dripping’ and suet have gone out of fashion.
Currently this work has only been done with mice but it is an interesting indicator of potential underlying causes around the obesity epidemic and useful for clients who have metabolic markers such as high triglycerides or diabetics who are struggling to lose weight despite doing ‘everything right’.
It is also worth noting that lard and chicken fats are not considered good sources of stearic acid due to the high levels of corn and soy usually fed to these animals, which causes their fat to become unnaturally high in linoleic acid (as their feed is not a species appropriate diet). This is also worth bearing in mind when making dietary recommendations around weight loss by ensuring clients are advised to source meat from farms where they are fed species appropriate diets.