Fat is not popular. We don’t want it on our body because it’s unsightly, and we don’t want it in our food, because it makes our bodies fat and sick. Or so we thought. Lately, fat has had bit of an image makeover, and that’s a good thing.
We need fat inside and around our bodies and in our diet. ‘Essential’ fats are called that, because they need to be part of our diet. The body cannot manufacture them. (The same is true for proteins: Proteins consist of varying combinations of 20 amino acids, 9 of which are essential. Before you ask: No, there are no essential carbohydrates.)
But where does fat actually go?
Let’s start with the fat that we can see and feel, or some of it at least: adipose tissue. It is distributed around our bodies in different ways, depending on whether we’re male or female. In women, it tends to be distributed around the thighs and bottom, in men it tends to accumulate more around the middle and abdomen, but this is not necessarily written in stone. Where we accumulate fat matters to our health as well: Abdominal fat (the fat around the middle) and visceral fat (the fat around the organs) are now known to be detrimental to health whereas fat around the thighs and bottom is considered benign. In other words: Being pear shaped is healthier than being apple shaped. But we need some fat! Adipose tissue insulates us, protects our internal organs and cushions our bones.
Fat cells also store energy for us. If necessary and depending on the amount of fat we carry, we can survive on those energy stores for quite a long time. For many years scientists thought that that is all it does, and it's a function that we should appreciate. We need to store calories in order to be able to sustain our greedy brains. Our brains are very large in comparison to our size, and to sustain a human brain requires a large amount of calories. Throughout most of the history of humanity, there was never a guaranteed safe calorie supply, and our adipose tissue is there to keep us going in lean times.
It was only fairly recently, in 1987, that research revealed that fat cells don’t just sit there doing nothing much (apart from the above), but that they actually manufacture steroid hormones (including oestrogen and testosterone). In 1994, it was discovered that adipose tissue also makes hormone-like substances called adipokines, which can act no only inside the cell they were made in and its immediate vicinity, but also around the whole body including the central nervous system. Together, hormones from adipose tissue and adipokines influence appetite and energy balance, insulin sensitivity, immunity, blood pressure, blood vessel formation, lipid metabolism, bone health and even reproduction. Adipose tissue is now recognised as an endocrine (ie hormone-producing) organ, and considering how many bodily functions are influenced by the hormones made in fat cells, it is not surprising that carrying too much or too little body fat has profound effects on our health. For more on those health effects, read Nutrilicious News, my newsletter which is due out tomorrow. It is not too late to subscribe!
Body fat is necessary to sustain life and the ability to reproduce. The ideal body fat percentage varies according to sex, age, and activity level. It can be measured using calipers, bioelectrical impedance analysis, a Bod Pod (a machine used at health centres) or DEXA Scanning, an X-ray method. All of these methods have their advantages and disadvantages. The last two are the most accurate, but are also the most expensive and least accessible. I offer bioelectrical impedance analysis at The Body Matters in Leigh-on-Sea, so if you are curious about your body fat percentage, why not book in with me?
Fat's other essential jobs
The brain consists of 60% fat, 25% of which is cholesterol. Fat also coats all other nerve cells around the body, forming the myelin sheath, which acts like the insulation around electrical cables, making sure nerve impulses can go where they are meant to go and not all over the place. But fat does not only make up the insulation, it is also an essential part of every cell wall. That is every cell wall, not just the walls of nerve cells.
The better the quality of fats you put into your body, the better the material your body has to work with. Unsaturated fats enhance the flexibility of cell walls, and flexible cell walls are what you want, because there is a lot of traffic into and out of cells. Flexible cell walls are what keeps your skin supple, your hair shiny, your heart beating strongly, your joints moving, your gut wall healthy, and much more. Having said that, cell walls can’t be too flexile either, or the cell might fall apart. Saturated fats provide stability, cholesterol has the job of keeping cell wall fluidity just right. Fats are not only a vital component of the membranes that form cell walls, but also the membranes of cell organelles, tiny structures inside each cell which perform vital functions, including the nucleus and mitochondria.
Cholesterol – a fatty substance, which really deserves its own blog post one day – is secreted by glands in our skin as sebum, which ensure that we remain waterproof, protects us from drying out when exposed to sun and wind and strengthens the skin’s barrier function that keeps undesirable microbes out.
So, be thankful for your fat. It provides essential functions without which we could not live.
There's much more to say about fat. Today's post was about fat in our anatomy. Watch this space for further posts about fat in our physiology, fat in our diet, and fat in our kitchens.