For many years there have been intensive studies in dietetics concerning the issue of nutrition factors, which influence most the increase of body mass. Of course, that one, who thinks that there is only one main factor while others don't matter, is naïve – unfortunately, it's not like this, however, among many various factors there are also those, which may really matter. And here we come to the properties of trans isomers of the fatty acids of industrial origin, which – attention - “fatten” more than other components of foodstuffs, even without difference in energy value!
The complexity of the lipids' nature
Fats, which we eat every day have different structure, which also influences their physical properties and biological activity. To make it simple, it can be said that some lipids are more and other are less wanted components of diet. Of course, in case of many fatty acids, this aspect should be considered in particular context, however, there are some fats, which are threatening for us in each case and – probably – in each dose (whereas, what's obvious, the more of them we eat, the worse it is for us). I am writing about trans isomers, obviously.
Fats, which are present in foodstuffs, are usually in a form of triglycerides, i.e. the glycerol esters and three rests of fatty acids. And these fatty acids are of various structure. This is how they differ among one another with the following features:
the presence of double binding – those, which have it are called mono- or polyunsaturated, and those, which don't have it – are called saturated,
the length of the carbon chain – we know short-, moderate- and long-chain fatty acids, the latter are in the biggest amount in our diet,
spacial configuration – and this is the heart of the matter: there are “cis” and “trans” fatty acids. The first ones dominate in the foodstuffs we eat, the others are almost impossible to find in nature – they are usually created during industrial processing of plant oils.
Trans isomers and health
As long as in the matter of the influence of saturated, or mono- and polyunsaturated fatty acids we are able to discuss and, depending on the context, disagree about the optimal intake and their influence on health, in case of trans isomers of industrial origin we know that it's simple: they are harmful even in small amount. It's officially advised not to cross the daily supply of 1% of the total energy intake, but it is getting more popular to state that it would be best to eliminate such acids from diet completely. Trans isomers are mostly created as a result of partial hydrogenation of plant oil and have wide use in food industry. They are mainly appreciated for the following features:
high thermooxidative resistance (the malicious one could say a joke that these fatty acids are already so unhealthy that they cannot become even worse because of high temperature),
solid state of matter in room temperature (i.e. it is a kind of oil with butter consistency),
low price (the cost of production of hydrogenated plant oil is ridiculously low),
the only problem with this kind of fat is that it is terribly harmful...
Trans isomers and body mass and composition
Trans isomers of industrial origin, apart from proven negative influence on cardiovascular system, also have many other unwanted properties. One of the shameful features of this kind of fat is its influence on body mass and composition. Research done on animals, which are much more related to humans than rats or mice, gives very interesting information. In the experiment on vervets (Chlorocebus aethiops), it turned out that trans isomers also fatten when the diet is adjusted to the energetic requirements of the body! The monkeys were divided into two groups. The first group was fed with diet, which included 8% energy from trans fatty acids, and the other was fed with diet including 8% of energy from the oleic acid. The calorific content of diets was adjusted in a way to cover the energetic demand of the animals (those were estimates, so they could include some mistake, but it's impossible to explain the results with such mistake). The study took 6 years. After that time it turned out that the monkeys, which were fed with hardened fats gained more fatty tissue than those from the control group. In the first case, the body mass increase was 7.2%, in the other it was only 1.8%. That's significant difference. What's interesting, it was observed, that visceral fat increased the most. Therefore, it's possible to state that trans isomers of fatty acids influence the chosen parameters in a way that even without increasing the supply of energy excessively, we may suffer from increased amount of fat! You can read more about this study here: