I thought you might be interested in this because almost no nutritionists or people involved in bodybuilding know this.
But in the world of aging and longevity research there is the knowledge that the lipid make up of the cellular membrane influences cellular metabolism. High DHA content in phospholipids of the cellular membrane is associated with high metabolic activity and this leads into the "membrane pacemaker" theory of metabolism.
This theory proposes that highly polyunsaturated acyl chains impart physical properties to cellular membrane bilayers that enhance and speed up the molecular activity of membrane proteins and consequently the metabolic activity of cells, tissues and the whole animal.
There is a positive correlation in the animal kingdom between body size and cellular metabolism with smaller animals possessing cellular membranes with higher DHA content and thus higher cellular metabolisms. Larger animals, humans for instance have cellular membranes with a lot less DHA and thus slower cellular metabolism.
All of this is correlated to lifespan. Highly polyunsaturated acyl chains (primarily DHA) are very susceptible to peroxidative damage. This kind of damage shortens lifespan.
The brain however is not correlated to any of this and in humans posses high DHA content in the cellular membrane & thus higher metabolism. It is thought that evolution probably weeded out those sluggish thought creatures that had slower brain cell metabolism.
How does it work? Well the physical properties of polyunsaturates primarily DHA are such that these lipid chains are flexible and active compared to unsaturated lipids. Because of the active or rapid movement of DHA lipids they exert lateral pressure on neighboring molecules in the cellular membrane. This creates greater activity in membrane enzymes, Na+/K+-ATPase molecules and thus ion channels become approximtely 25% more active. A large part of cellular energy goes into operating those channels.
Similar sorts of activity occur in the mitochondrial membrane proteins.
A good & recent review of all of this is The links between membrane composition, metabolic rate and lifespan
, A.J. Hulbert
, Comparative Biochemistry and Physiology, Part A 150 (2008) 196–203
Now we know from source material such as Evolutionary Aspects of Diet, the Omega-6/Omega-3 Ratio, and Gene Expression by Artemis P. Simopoulos
found in the book Phytochemicals: Nutrient-Gene Interactions
, Mark S. Meskin (Editor)
, CRC; 1 edition (February 22, Phytochemicals: Nutrient-Gene Interactions, Mark S. Meskin (Editor), CRC; 1 edition (February 22, 2006)
"... the polyunsaturated fatty acid (PUFA) composition of cell membranes is to a great extent dependent on the dietary intake."
So if you ingest a large quantity of Omega 3 fatty acids which contain high DHA content you will alter the makeup of the cellular membrane such that it is composed of more DHA which will increase cellular metabolism.
This is great for dieting but increases the potential oxidative damage. Enough to effective lifespan? Probably not. But it should increase energy expenditure and thus be beneficial on a diet.