If, like us, you're keen on living well and minimising your recourse to medical intervention for as long as possible, it’s important to understand the ways we use and store food as fuel. Doing this right helps us become lean and fit and, above all, healthy and doctor-free! It’s about taking back control of your health, whether you’ve already handed that responsibility to someone else or are worried it might happen in later life.
Having introduced the Food4Health Plate in our article on becoming more metabolically flexible, we now look at how we use and store the energy from that Food4Health Plate-inspired food plan. And in Getting Nutritionally and Physically Flexible, we continue this article to also touch on how particular sequences of food and activity can be combined for optimum results.
Getting it wrong
As a result of a 40 year-old mistake, we are currently eating way too many carbs and not enough fats. A paper published in early 2015 in the journal Open Heart has proven that the low-fat guidelines developed by the UK and US governments in the 70s and 80s had NO SCIENTIFIC BASIS and were WRONG, even with the knowledge available then. With today’s knowledge, it’s verging on criminal.
Consuming little fat and lots of carbs, especially refined ones, and even eating too much protein, stops us from becoming ‘keto-adapted’ (efficient fat burners). In a high-fat nutshell, the fact that we have allowed our ability to burn fat to become defunct is a major contributor to our present obesity and chronic disease epidemic.
Governments, most medical doctors, and especially Big Food and Big Pharma, aren’t telling this story - there’s too much money to be made from keeping us ill!
What’s your Fuel Consumption?
The human body has very intelligent systems for turning food into energy. It needs to power the metabolism, build new DNA and cells, run the brain and immune system (the two biggest energy drains), digest food and much more, all before any activity is considered to fuel the mitochondria and muscles!
Let’s look at carbs first, given that governments tell us they should represent the primary source of our energy.
Anaerobic glycolysis of one glucose molecule yields just two ATP molecules
Carbs are basically long chains, simple or complex, of glucose (a 6-carbon sugar). Using enzymes, our bodies create energy from glucose by splitting each molecule into two 3-carbon sugars. This ‘sugar-splitting’ process is called glycolysis. During anaerobic (without oxygen) glycolysis, each glucose molecule generates two molecules of ATP (adenosine triphosphate – cellular energy) and two molecules of pyruvic acid (pyruvate).
To put this amount in context, we need at least half our bodyweight’s-worth of ATP a day, just to function!
But, Aerobic glycolysis of each glucose molecule yields 34 ATP molecules
If you are not exercising near your limit, exceeding your lactate threshold, you burn your carbs via aerobic glycolysis (with oxygen). Here, the pyruvate is converted to acetyl co-enzyme A (often referred to as acetyl-coA), a key component in the Kreb’s cycle (our mitochondrial energy-generating process).
You may only get 2 ATP molecules directly from Krebs (used mainly to generate energy carriers like NADH and FADH), but Kreb’s metabolites, along with various cofactors including co-enzyme Q10, are the key drivers for the whole electron transport system (ETS), which is the main way we get energy from food. And when we oxidise glucose in the presence of oxygen we get a somewhat impressive 34 molecules of ATP for each molecule of glucose.
Our bodies can only store a limited amount of glucose (as glycogen): around 100 grams in the liver and about 400 grams in the muscles. In the absence of other fuel, most people have burned these glycogen stores up after around 90 mins of strenuous activity.
What about proteins and fats?
They also get oxidised to create ATP – and also play a part in the Kreb’s cycle. Proteins must be broken down to their constituent amino acids (20 in total), and have their nitrogen removed before being used directly or indirectly in the Krebs cycle. Glutamate is also a critical player because it is the key transporter of amino acids in the blood, amongst other key functions like helping to maintain integrity of the intestinal lining and supporting the immune system and kidneys.
Gram for gram, protein yields about the same amount of energy as carbohydrates. You’ll see on food labels that 4 calories (kcal) are yielded for every gram of carb or protein contained in a food. However, that’s the case only if you both absorb and oxidise the fuel fully. Unfortunately, many of us don’t digest, absorb or oxidise our fuels fully because of one or more genetic or physiological impairments.
But we’ve left the best to last!
“One molecule of fat yields…..how many ATP molecules?”
Fats yield energy from oxidation too and the products of this oxidation, just like carbs and protein, converge on the Kreb’s cycle. Fats are broken down to their constituent fatty acids via the beta-oxidation pathway, mainly in the liver. They then yield the common denominator acetyl-coA via 4 reactions that occur in the mitochondria and peroxisomes, mainly in the liver and muscles.
If you take just one molecule of a fatty acid, say palmitate, you can generate a stunning theoretical yield of 129 ATP molecules using the beta-oxidation pathway! This makes even that 34 ATP yield from aerobic glucose glycolysis look paltry.
But that’s not all. If you limit your intake of carbs, but increase your need for energy (i.e. through exercise), more acetyl-coA will be produced from the beta-oxidation of fatty acids. If you don’t use it all, the excess acetyl-coA is shunted into another process called ketogenesis or ketosis that yields ketone bodies (acetoacetate, β-hydroxybutyrate and acetone), which then become an additional metabolic fuel.
From an evolutionary perspective, this pathway is clear evidence for just how well we are adapted to starvation, or what we now think of as ‘intermittent fasting’ (i.e NOT three meals a day with snacks in between). Without food, we can actually use ketone bodies produced by beta-oxidation of our own fat deposits as our primary fuel for vital organs such as the brain and heart. BUT, don’t get carried away: do it for too long and raise your ketone levels too high, you….die.
For a long time, scientists and doctors thought of ketosis as a bad thing because it was associated with either starvation, or uncontrolled diabetics, who can develop serious and life-threatening diabetic ketoacidosis.
But, as shown by Drs Jeff Volek and Steve Phinney in their bestselling book, The Art and Science of Low Carb Living, healthy, nutritional ketosis can be established when concentrations of ketone bodies in the blood are in the range 0.5-3.0 mM: the “optimal ketone zone”. This can be achieved with a low carb, relatively high fat, ketogenic diet, such as that consumed when you follow the Food4Health Plate. It is also possible to measure your level of nutritional ketosis simply and easily through urine, blood or more recently breath testing, using a Ketone Meter.
Do beware, though: if we don’t have enough carbs in our body, and we haven’t adapted to burning fats though the fatty acid-burning beta-oxidation pathway, our bodies will start to burn the protein in our muscles for energy. This is never a good thing, especially if you’re interested in improving your lean muscle mass and being physically very active.
We’re all aware of how readily our bodies store fat. We also know that the main reason people get fat is not from eating too much fat, but by eating too much carbohydrate. Fat can exist in many forms and is stored in different ways and places, including beneath the skin (as adipose tissue) or around the organs (as visceral fat). Generally the latter is the most dangerous and needn’t be that visible, hence recent concerns about the risk of being ‘skinny fat’ i.e. thin on the outside, fat on the inside. This is an increasingly common predicament triggered by low fat recommendations which have led to dependence and addiction to refined carbs from soft drinks, white bread and other ultra-processed, high glycaemic foods.
A bit of brown adipose tissue (BAT) or brown fat, on the other hand, is the healthiest fat to lay down. It becomes a key fuel if you are keto-adapted and want the stamina of an endurance athlete.
Putting it all into practice
Having understood how our bodies process food for fuel, the vitally important connection to make is to understand that physical exercise has a HUGE bearing on HOW this happens. Please continue to Getting Flexible Nutritionally and Physically for an indepth look at this.
This article has been adapted from a previous article by Robert Verkerk PhD from the website www.anh-europe.org