Fast food and you: The effects of too much fat, sugar, and salt in your diet

With obesity rates rising and fast food chains profiting, Dr Nick Knight looks at what all of this fast food is really doing to our bodies

I try to hasten my pace past the neon-glow of the user-friendly menu, but the aroma has already conga-lined up my nose and trapped me. The environment screams innocence and ease, with its doors wide open and welcoming, like a hippopotamus lying in wait. I go in, order, and consume my burger and fries within 60 seconds of pure sensory joy – followed, by half an hour of indigestion.

Fast food is anchored firmly in our fast-paced world, providing us with the food aligned to the modus operandi for modern living - quick, easy and cheap. The effects on your body, however, are not as innocent.

Now we all know that fast food is tasty because it is packed with sugars and fats. It is also apparent that sugar is currently monopolising the limelight, with media and health groups holding their pitch forks aloft, and burning effigies of sugar cubes at dawn, calling for ‘sugar taxes’ and reform. With this in mind, I am going to focus my article on the saturated and trans-fats lurking in our fast food, and provide a snapshot of their unscrupulous activity in your body.

But before I sharpen my pitch-fork and strike-up my matches, I want to explain why fat, especially the healthier unsaturated fats that you get from foods like oily fish, are actually a welcomed, necessary component of your balanced diet. Let us begin with the big picture reasons first: protection, insulation and fuel.

Fat is your body’s natural cushion, providing protection and comfort for your internal organs and pressure areas like your bum (sitting on the ‘ischium’, a part of your pelvis, without any fat is not nice). Fat also provides you with some natural minor insulation, so that once our British summer has completed its annual 14 day stint, it supports your body’s thermoregulation.

Last but by no means least, your body fat acts as an impressive energy depot, with around 100,000 calories available for your body, if called upon. This, by comparison, dwarfs your quicker release carbohydrate stores that limp in at a weak second place, providing around 1900 calories – about 24 hours worth. So, if you are wondering how Tom Hanks survived in Castaway, no, it wasn’t just the company of Wilson that kept him going but that unsung hero, fat.

The positive roles of fat in your body - such as supporting the digestion, absorption, and transport of your fat-soluble essential vitamins A, D, E and K; and its secretion of the hormone, leptin, which acts as a ‘fat thermostat’ (or a ‘lipostat’) to regulate your body habitus by effecting your hunger – indeed, do go on. However, it is time to tool-up and light the match…

Fast food fats have the potential, when consumed in excess (Government daily recommendations are less than 20g for women and 30g for men of saturated fats, and less than 5g trans-fats for both) to deliver both troublesome short-term problems and more alarming long-term repercussions to your health. After-all, every bite adds up, with a fast food burger packing about 10g of saturated fat, and a quarter of your recommended calorie intake for the day (and that’s before you factor in the fries and fizzy drink!).

So, let us consider your brain for a moment. Now although with a mass, attributing only 2% of your body’s total, your brain has a staggeringly disproportionate metabolic demand, accounting for 25% of your total energy consumed. It needs this in order to allow you to make those smart business decisions, witty Facebook status updates, and think with clarity. “But you said fats have loads of energy!” I hear you shout. Sadly, like a disappointed under-18 at a night-club, the fats just can’t get in; the interface between the brain and the blood stream being largely (but not entirely) impermeable to fat. Quite simply, your brain needs carbohydrates for fuel.

To be honest though, a few dumb days are not your main concern. Instead it is the long-term risks of a fast food, high-fat diet lifestyle that are more worrisome. You only need to look around, or down at yourself, to see that we are an expanding society with over 64% of adults in the UK overweight or obese. It goes without saying that this carries significant mortality and morbidity risks. Yes, I agree, this is a product not just of a poor diet but of chronic physical inactivity (and numerous other factors) – but that is a story for another day.

Now before we move on, I want to clarify the two main types of fats in your body; you have ‘subcutaneous fat’ (some, admittedly more than others), which consists of fat cells called adipocytes, deposited under your skin in an area called the hypodermis and gives us all our, well, unique shapes, paving the way for the colourful phrases like ‘love handles’. Then, there is your ‘visceral fat’ which surrounds your organs. Depression, osteoarthritis, gout and increased infection risks are all associated with excess fat consumption and weight gain. Although both carry their own set of risks, when in chronic excess, visceral fat is by far more concerning both by its insidious existence and its consequences, so we shall focus on these.

So let us start with the more serious of the two - visceral fat, the fat that is packed between our organs. Excessive consumption of fast foods will chronically elevate the levels of fats in your blood. Alongside this, the amount of ‘bad’ cholesterol-carrying molecules, known as low density lipoproteins (LDL), also increases. This is bad news for you, as instead of helping to remove cholesterol from your body, the LDL carts it off to sites such as your liver and the walls of your blood vessels. The end result is that your blood vessel walls develop fatty plaques, in process known as atherosclerosis, narrowing them over time. This elevates your risk of interrupting blood supply to major organs like your heart and brain, increasing the risk of conditions like angina, myocardial infarctions (‘heart attacks’) and cerebro-vascular events (‘strokes’).

Organs, particularly your liver can also become infiltrated with fat. This is a gradual process that may begin with a ‘fatty liver’ but progress, over a lifetime, to conditions more serious such as non-alcoholic steatohepatitis (NASH), causing inflammation and damage to your liver. Excess fat can further unremorsefully impair your body’s sensitivity of peripheral tissues to insulin, causing type two diabetes. An excess of fat in your diet may also endorse the ‘metabolic syndrome’, a collection of conditions that includes hypertension (high blood pressure), diabetes, obesity, and hypercholesterolemia (high cholesterol), all present in one person. This can ultimately, as a result of dysregulation in energy usage and storage, greatly increase the risk of cardiovascular disease.

Now, I am going to break my promise to the salts and sugars, and very briefly give you a snap-shot of role in this fast food debate. The best way to explain the role of sugars is to talk about the ‘crash’. Not the Academy Award winning movie, no, but the feeling you get after you have demolished your fast food meal in record time, and then 60 minutes later slip into an exhausted, sluggish, and lethargic ‘food-coma’ to rival Sleeping Beauty. The simple, refined sugars in these foods give your blood sugar levels a huge, immediate spike – giving you that burst of energy – before being used up almost immediately. This is why you are left craving more – you are, in part, addicted to the sugar; just like kids and sweets.

High salt levels in fast food (roughly 2g in a fast food burger alone, equalling one third of your maximum daily allowance) can leave you feeling thirsty in the short term - but in the long-term can affect your blood pressure and subsequent risk of future cardiovascular disease.

The way in which high salt levels do this is, once in your blood stream, it separates into sodium and chloride, increasing the pressure in the blood by ‘holding water’ in you blood stream, and thereby exerting more mechanical stress on your blood vessel walls. A diet with chronically excessive salt will worsen blood vessel wall damage and promote hypertension.

Of course, the jackpot question is “why do you like fast foods so much?” As with most answers I give, there are, frustratingly, multiple factors – two of which I will highlight. Firstly there is that perfect combination of fats, sugars and salts in foods (that fast food companies look to perfect) that galvanises your brain’s reward centre; and secondly the orosensation (i.e. how the food feels in your mouth) and mouth-watering taste; both of which leave you craving more of the same guilty fast food pleasure.

As we draw to a close on this debate, cast your mind back to what I said in the beginning – some fat, the right fat, is good for you. It is a natural, supportive and healthy part of your diet. Just, perhaps, be mindful to select out the less desirable saturated- and trans-fats, high salts, and sugars that are within fast food. The NHS ‘Live Well’ website, for example, has mountains of information to help.

Remember too that the occasional fast food meal isn’t going to hurt you (I certainly have the occasional one), it is more that the cumulative effects of three or four each week will increase your health risks. I too appreciate that fast food chains do seem to be trying to become healthier – which is commendable. As always, if you are concerned about anything raised here, for example, your eating habits, want support for weight management, or further information on the health effects of high-fat diets, then please contact your GP - they are there to help.

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