What is metabolism? Is metabolism genetic? Can knowing more about your metabolism help with weight loss? Generic advice on what to eat and drink is indeed a thing of the past. Today, modern DNA test kits can analyse your metabolism in such a way that can help you immensely when it comes to adopting a diet and workout plan tailored to you, based on your own genetics.
Are you more of a carbohydrate type of person? Or do you prefer the fattier foods? Not sure? According to scientists, this information can be found in your DNA. Everyone has a different metabolism, everyone processes carbohydrates and fats differently, and everyone loses and gains weight differently.
Did you know that between 40 and 70 per cent of weight differences between people are down to their genes? Analysing your metabolism with a DNA test can therefore reveal all-important insights into how your body reacts to certain foods, how hungry you are and which sports are most suited to you individually. This information will then help you decide on which diet is best for you: low-carb, low-fat, protein or a mixed diet.
So, read on to find out what ‘metabolism’ really means, which metabolism theories exist and which particular genes scientists look at to understand differences in our metabolisms.
What is metabolism?
Encyclopedia Britannica defines ‘metabolism’ as the chemical processes that occur in living organisms which create energy or new organic material. In layman’s terms, you could summarise ‘metabolism’ as follows:
Where chemical substances are transformed in your body, metabolism takes place.
Metabolism is one of the most unique phenomena that all living organisms possess – from bacteria and mushrooms and plants to humans and other animals. With energy metabolism, we can take in energy from our surroundings – especially through our diet – and use it in our bodies. Only then can we move, think, develop and reproduce.
Perhaps, you’ve already come across the concept of thermodynamics. If so, you are most likely aware that energy forms can never be destroyed or lost – they can only be transferred or transmitted. This is also applicable to the metabolism processes occurring in our bodies. The energy we absorb from our food is converted into other forms of energy in our bodies. It is the energy we use for our muscles, brain and other organs.
Why analyse metabolism?
Scientists are now confident that metabolism changes from person to person. What your body recognises as good nutrients also influences your ability to gain and lose weight as well as how your muscles work.
Metabolism tests can therefore deliver exciting and insightful findings, such as which foods are best suited to you – if you want to lose weight – and how strongly you are affected by feelings of hunger or fullness. Whether you are suited to weight training or endurance sports may also come to light with a metabolism test.
This is why weight loss and sports programmes often come about after taking metabolism tests.
The evolution of the metabolism gene
How and why is it even possible for two different people to have a completely different metabolism to each other? Some biologists believe that, over the process of evolution, various metabolism types came into existence.
Our ancestors were, for the most part, hunters-gatherers. They predominantly ate meat, berries, nuts, fruit and herbs. The amount of fat and protein in their diet was probably higher than what we consume in our Western diets today. It was only around 10,000 years ago that humans in Europe started to cultivate grains and consume a far greater amount of carbohydrates. Although this change seems like ancient history, in terms of evolution, this was really not too long ago.
Some experts believe that this is why the genes of many people today are still adapted to fat and protein utilisation – these people would therefore be more susceptible to gaining weight after consuming carbohydrates. For others, their genes have adapted far better to carbohydrate utilisation over the last 10,000 years.
Experts agree that our evolved bodies can’t have already adapted to diets that have emerged over the past 100 years. Processed foods, sugar and too many calories generally lead to civilisation diseases, such as obesity, diabetes and high blood pressure.[2, 3]
From the Stone Age to the science we know today
Of course, we don’t know exactly what our ancestors ate more than 10,000 years ago. Experts have, however, studied beings that lived in the age of the hunter-gatherers. These hunter-gatherers rarely ever had heart and circulation problems. They ate considerably more protein (19 to 35 per cent) and less carbohydrates (22 to 40 per cent) compared with today’s Western diet. They consumed a similar amount of fat (28 to 58 per cent) – but most likely more healthy omega-3 fatty acids. This could explain why their heart and circulation system was so healthy.
Other experts believe that the carbohydrates humans ate during the Paleolithic Age were of a higher quality. During this historic period, carbohydrates originated from fruit and vegetables and rarely from grains; humans during this era ate a large amount of fibre.
Analysing metabolism through DNA test kits
Our genes are the basis of all processes that take place in our bodies, including all metabolic processes. Over the last few years, experts have discovered more and more genes that are linked to obesity and our ability to lose weight.
If you have metabolism genes analysed with a DNA test, you could find out the following:
- how prone you are to accumulating unwanted fat when consuming fats and carbohydrates;
- how strongly you feel hunger and how quickly you become full;
- how quickly your muscle fibres contract – and therefore which sports are best suited to you
Can you inherit the ‘fat gene’?
Of course, genetics are not the only components responsible for obesity. However, a tendency to be overweight can be passed on genetically through your DNA.
Scientists have been able to look at this link more closely in a large study published in the renowned journal Nature. The experts evaluated 125 studies with data from almost 340,000 people.
When they did this, they found 97 genes that were connected with weight. Together, these genes would explain 2.7 per cent of the weight difference between the people studied.
In total, DNA influences weight to a far greater extent: 40 to 70 per cent of weight differences between people lie hidden in their DNA.
How do our genetics influence weight?
Our genetics control metabolism and weight in various ways. For one, they decide how effectively our digestive systems metabolise carbohydrates, fats and proteins, respectively.
That’s not all though – genes also control our eating behaviours. For example, how frequently do you feel hungry? How quickly do you feel full after eating? Do you have a tendency to binge-eat or comfort eat?
Which genes control metabolism and obesity?
What is particularly clear is that there is a correlation between the FTO gene and obesity. FTO is even aptly named after this link, standing for ‘fat mass and obesity-associated’.
People with a particular variant of the FTO gene in their DNA sequence were more likely, according to studies conducted, to have a higher body mass index (BMI). In summary, it seems that the FTO gene determines whether you gain weight quickly.
Experts saw this effect especially in people who had the FTO gene variant and also consumed lots of fatty foods. Such foods particularly include saturated fatty acids, which are found in convenience goods and animal products, such as meat, milk and cheese.
Some medical experts have subsequently concluded that FTO determines whether some people are more likely to gain weight when consuming fat. A low-carb diet, which is predominantly based on fat, is therefore not ideal for these people.
To some extent, the FTO gene also determines how well we manage our eating behaviours. In a particular study, children and young people with the FTO gene variant were more likely to have uncontrolled binge eating episodes and also a higher BMI and body fat percentage.
Are there other ‘fat genes’?
Of course, numerous other genes have a role to play in your DNA. The link between the FTO and APOA5 genes appears to partially influence the likelihood of obesity and high blood pressure.
APOA5 is another gene that similarly determines how exactly your body utilises fat and how quickly you gain weight.
The PPARG gene is yet another gene linked to your weight. A variant of this gene would potentially explain why some people are more likely to gain weight by consuming fatty acids.
Table: Eight genes that are connected with your metabolism [7–9] [11–14]
What they influence
Sensitivity to fat, weight loss by reducing calorie intake, tendency to be overweight
Sensitivity to fat, weight loss by reducing calorie intake
Feeling of hunger, sensitivity to fat, tendency to be overweight, tendency to snack and consume meals rich in calories
Sensitivity to fat, weight loss due to sports, weight loss by reducing calorie intake, tendency to be overweight
Activation of leptin, the ‘hunger hormone’
Muscle fibre contraction speed
How is metabolism analysed with a DNA test kit?
DNA tests use complex laboratory diagnostics, but are in principle very easy to carry out. You just need to take a saliva sample using a swab and insert it into a sample tube.
This is how a metabolism test typically works. A specialised laboratory will analyse your saliva sample and look at various genes that are relevant to your metabolism, including the FTO, APOA5 and ADRB3 genes.
After the analysis is complete, you tend to receive the following insightful information:
- Whether you tend to gain weight by consuming carbohydrates or fat
- Whether you tend to get really hungry or full quickly
- Which muscle fibre type and endurance type you are and which sports are best suited to you
Metabolism test: other theories and testing methods
Over the last few decades, scientists have tried, time and again, to categorise different metabolism types in various people without analysing DNA samples. Some of these analyses are still used in practice today; however, most of these have, scientifically speaking, been outdated for years.
Sheldon’s theory on types of metabolism and physique
An old-fashioned method of categorising the metabolism of different people is by metabolism type or physique type; this was a suggestion made by American psychologist and physician William Sheldon. His metabolic categories are sometimes still used today in the fitness industry in order to describe particular physique types.
Sheldon believed that it was possible to infer a person’s personality from their physique – and thereby identify people who were more likely to become criminals purely based on their appearance. This questionable theory was controversial – even back in the 1940s when Sheldon published it. Since then, his theory has been disproven in the sciences.
The physician distinguished between three types of people based on their physique and metabolism, amongst which you can also identify mixed groups:
- Ectomorph: tendency to be slim and fine-boned
- Mesomorph: tendency to be muscular
- Endomorph: tendency to be ‘rounded’ or obese
Caution: These categories are outdated! Sheldon never conducted scientific studies to support his theories. From a scientific point of view, body physiques are of little significance.
Kelley and Wolcott and metabolic typing
An alternative medical method of analysing metabolism is known as ‘metabolic typing’ – a method created by the US orthodontist William Donald Kelley and novelist William Linz Wolcott. However, Kelley and Wollcott never presented any findings or studies to support their theory. Wolcott has instead been marketing his theory with his company Healthexcel since 1987.
When it comes to metabolic typing, the following aspects of metabolism are observed:
- The nervous system’s influence: parasympathetic (calming) or sympathetic (stimulating) type
- Fast (gluco type) or slow (beta type) fat burning
- The gland – whether thyroid, pituitary, adrenal or (for women) ovaries – with the greatest influence
These aspects should give you clues as to which foods you should eat in order to lose weight and maintain a healthy body weight.
There is no standard way to determine your metabolism type. Consultants and holistic practitioners offering metabolic typing as a service take various measurements when they conduct metabolism tests. Methods include questionnaires, body fat analyses, using electromagnetic diagnostic equipment, and blood and urine samples are also carried out.
Some would say that there isn’t any scientific reason to carry out metabolic testing. The fact that many people do indeed lose weight whilst on this diet is easy to explain: by changing your diet, you are automatically more conscious of what you eat and therefore consume less calories.
Metabolism test – at a glance
What is metabolism?
Metabolism – or energy metabolism – refers to processes in the body, during which various substances are converted into one another. We absorb energy through our diet, and this energy is transformed in our bodies to be used in all kinds of processes.
What will a metabolism test achieve?
If you find out the characteristics of your metabolism with a DNA test, for example, you can adapt your diet and sports programme to complement your genetics. Doing this could help you significantly to reach and maintain a healthy body weight.
How are genetics and metabolism linked?
Our DNA also determines how we use the nutrients we consume and our behaviour when it comes to food. Scientists have also discovered particular genes that are linked to how much weight we gain through consuming fat and carbohydrates, how strong our hunger is, how full we feel after meals and how quickly our muscle fibres contract.
How does a metabolism analysis work with a DNA test kit?
For a DNA test, a saliva test is generally taken from the oral mucosa – the inside of your mouth. Specialised laboratories then look for particular genetic traits that should be analysed. Doing this, you can find out, for example, whether the FTO gene has mutated, making you more susceptible to weight gain and a diet that is rich in fat.
 Encyclopedia Britannica, ‘Metabolism | Definition, Process, & Biology’, Encyclopedia Britannica. [Online]. Available at: https://www.britannica.com/science/metabolism. [Accessed: 8 January 2020].
 L. Cordain et al., ‘Origins and evolution of the Western diet: health implications for the 21st century’, Am J Clin Nutr, vol. 81, no. 2, pp. 341–354, Feb. 2005, doi: 10.1093/ajcn.81.2.341.
 M. Konner and S. B. Eaton, Paleolithic nutrition: twenty-five years later“, Nutr Clin Pract, vol. 25, no. 6, pp. 594–602, Dec. 2010, doi: 10.1177/0884533610385702.
 L. Cordain, S. B. Eaton, J. B. Miller, N. Mann and K. Hill, ‘The paradoxical nature of hunter-gatherer diets: meat-based, yet non-atherogenic’, Eur J Clin Nutr, vol. 56 Suppl 1, pp. 42–52, March 2002, doi: 10.1038/sj.ejcn.1601353.
 A. E. Locke et al., ‘Genetic studies of body mass index yield new insights for obesity biology’, Nature, vol. 518, no. 7538, pp. 197–206, Feb. 2015, doi: 10.1038/nature14177.
 D. Corella et al., ‘A High Intake of Saturated Fatty Acids Strengthens the Association between the Fat Mass and Obesity-Associated Gene and BMI123’, J Nutr, vol. 141, no. 12, pp. 2219–2225, Dec. 2011, doi: 10.3945/jn.111.143826.
 M. Tanofsky-Kraff et al., ‘The FTO gene rs9939609 obesity-risk allele and loss of control over eating’, Am. J. Clin. Nutr., vol. 90, no. 6, pp. 1483–1488, Dec. 2009, doi: 10.3945/ajcn.2009.28439.
 M. H. Wang et al., ‘Four pairs of gene–gene interactions associated with increased risk for type 2 diabetes (CDKN2BAS–KCNJ11), obesity (SLC2A9–IGF2BP2, FTO–APOA5), and hypertension (MC4R–IGF2BP2) in Chinese women’, Meta Gene, vol. 2, pp. 384–391, May 2014, doi: 10.1016/j.mgene.2014.04.010.
 C. Sánchez-Moreno, J. M. Ordovás, C. E. Smith, J. C. Baraza, Y.-C. Lee and M. Garaulet, ‘APOA5 Gene Variation Interacts with Dietary Fat Intake to Modulate Obesity and Circulating Triglycerides in a Mediterranean Population12’, J Nutr, vol. 141, no. 3, pp 380–385, March 2011, doi: 10.3945/jn.110.130344.
 J. A. Martínez, M. S. Corbalán, A. Sánchez-Villegas, L. Forga, A. Marti and M. A. Martínez-González, ‘Obesity Risk Is Associated with Carbohydrate Intake in Women Carrying the Gln27Glu β2-Adrenoceptor Polymorphism’, J Nutr, vol. 133, no. 8, pp. 2549–2554, Aug. 2003, doi: 10.1093/jn/133.8.2549.
 K. Masuo, ‘Roles of Beta2- and Beta3-Adrenoceptor Polymorphisms in Hypertension and Metabolic Syndrome’, Int J Hypertens, vol. 2010, Oct. 2010, doi: 10.4061/2010/832821.
 D. Corella et al., ‘Association between the APOA2 promoter polymorphism and body weight in Mediterranean and Asian populations: replication of a gene-saturated fat interaction’, Int J Obes (Lond), vol. 35, no. 5, pp. 666–675, May 2011, doi: 10.1038/ijo.2010.187.
 L. M. Delahanty et al., ‘Genetic predictors of weight loss and weight regain after intensive lifestyle modification, metformin treatment, or standard care in the Diabetes Prevention Program’, Diabetes Care, vol. 35, no. 2, pp. 363–366, Feb. 2012, doi: 10.2337/dc11-1328.
 M. Lefevre et al., ‘Comparison of the acute response to meals enriched with cis- or trans-fatty acids on glucose and lipids in overweight individuals with differing FABP2 genotypes’, Metab. Clin. Exp., vol. 54, no. 12, pp. 1652–1658, Dec. 2005, doi: 10.1016/j.metabol.2005.06.015.
 J. E. Roeckelein, Dictionary of Theories, Laws, and Concepts in Psychology. Greenwood Publishing Group, 1998.
 ‘Metabolic Typing - Home’. [Online]. Available at: http://www.healthexcel.com/index1.html. [Accessed: 09 January 2020].