Carbohydrate digestion and obesity strongly linked

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New research indicates that obesity in the general population may be genetically linked to how our bodies digest carbohydrates. People usually have two copies of the gene AMY1, but in some regions of our DNA there can be variability in the number of copies a person carries, which is known as copy number variation. The number of copies of AMY1 can be highly variable between people, and it is believed that higher numbers of copies of the salivary amylase gene have evolved in response to a shift towards diets containing more starch since prehistoric times.

New research indicates that obesity in the general population may be genetically linked to how our bodies digest carbohydrates.

Published today in the journal Nature Genetics, the study investigated the relationship between body weight and a gene called AMY1, which is responsible for an enzyme present in our saliva known as salivary amylase. This enzyme is the first to be encountered by food when it enters the mouth, and it begins the process of starch digestion that then continues in the gut.

People usually have two copies of each gene, but in some regions of our DNA there can be variability in the number of copies a person carries, which is known as copy number variation. The number of copies of AMY1 can be highly variable between people, and it is believed that higher numbers of copies of the salivary amylase gene have evolved in response to a shift towards diets containing more starch since prehistoric times.

Researchers from Imperial College London, in collaboration with other international institutions, looked at the number of copies of the gene AMY1 present in the DNA of thousands of people from the UK, France, Sweden and Singapore. They found that people who carried a low number of copies of the salivary amylase gene were at greater risk of obesity.

The chance of being obese for people with less than four copies of the AMY1 gene was approximately eight times higher than in those with more than nine copies of this gene. The researchers estimated that with every additional copy of the salivary amylase gene there was approximately a 20 per cent decrease in the odds of becoming obese.

Written By: Science Daily
continue to source article at sciencedaily.com

9 COMMENTS

  1. The interesting thing about a finding such as this is that it provides a scope for gene therapy as a treatment, similar to one for cystic fibrosis. One of my school biology teachers claimed the mutation responsible for CF was the most common deleterious mutation in humans, but it would be unsurprising if one or more single-gene changes could tackle obesity in millions of people worldwide. My teacher explained that the prevalence of the condition and the simplicity of the required genetic change motivates CF as one of the major things to treat with gene therapy. If you could similarly deliver multiple AMY1 copies to body cells, the benefits per unit cost could be sizeable. Having said that, the CF case has the benefit that the only cells that need to be modified are those of a single tissue that an inhaler can easily access. There may be other problems with following this route to tackle obesity too, but I’ll leave identifying those to other commenters.

  2. Very interesting, but what about simply changing the balance between consumption and expenditure of energy?

    I had acidosis until age ten or so, so was exceedingly skinny at the time when fat pads usually begin to form, and once formed they are extremely difficult to get rid of, and some people never manage it in there entire lives.

    So although I had to rest in the afternoons it turned out in the long run that I was fortunate.

    Despite our evolutionary need for fats and sugars, to this day I personally can’t stomach fatty foods, and I don’t like sugary stuff either.

  3. I admit to being a bit sceptical about this as a major cause of obesity in the general population.
    People have been eating carbs for a long time but the huge surge in obesity has only occurred in a relatively short time. There must be another factor at work in addition to a genetic explanation – like the increased amount of sugar in food.

    • Yes, sugar is the key. Complex carbs have been consumed for a long time. In its simplest form, sugar, never previously available to humans in quantities near those available now, not only primes your body for fat deposition by jacking up your glucose (which then jacks up your insulin in response, which is the most impactful part), it also taxes the pancreas with the repeated simple sugar charged hits we so often feed our nascent (evolutionarily speaking) bodies. The constant flow of insulin from sugar intake can cause weight gain in a number of ways, hence the close relationship between Type II diabetes and obesity (there are also other contributing factors of course).

      In reply to #4 by mr_DNA:

      I admit to being a bit sceptical about this as a major cause of obesity in the general population.
      People have been eating carbs for a long time but the huge surge in obesity has only occurred in a relatively short time. There must be another factor at work in addition to a genetic explanation – lik…

    • In reply to #4 by mr_DNA:

      I admit to being a bit sceptical about this as a major cause of obesity in the general population.
      People have been eating carbs for a long time but the huge surge in obesity has only occurred in a relatively short time. There must be another factor at work in addition to a genetic explanation – lik…

      We may well have genes that are linked with obesity but not all genes that lead to disease are necessarily expressed. The new emerging field of epigenetics studies the environmental factors that lead to the expression of such genes.

      When we examine the changes in the last 40 years to our diets in the context of human evolution we have not had time to adapt. As we emerged from the Paleolithic era 12,000 years ago as hunter gatherers, we settled and harvested the land. We gradually changed our natural diets. We ate foods that started to affect our health but found ways to make them more digestible such as fermentation and sprouting. We recognised the importance of nutrient rich foods and used them to nurture our young.

      The huge surge in obesity and chronic diseases such as cancer and cardio vascular disease started in the late 1970′s. This coincided with several significant changes in the western diet.

      Up until the 1960′s every woman knew that sugary foods and all types of carbohydrate (which are broken down into glucose in the blood stream) would make her fat. Men were encouraged to ‘Go to work on an Egg’. Any food that was fatty was referred to as ‘rich’ due to our innate understanding that fatty foods were a rich source of nutrients and energy. We cooked with butter, lard and shortening, we drank full fat milk. We were not obese in the shocking numbers we see today.

      In 1977 the American Government Senator George Mc Govern issued new Dietary Goals to encourage people to eat a Low Fat diet. This meant we had to increase our intake of Carbohydrates as an alternative source of energy. This advice followed two scientific studies.

      1) A study by Russian Scientists in 1913 examined rabbits. Despite being herbivores, they were fed large quantities of fats, not naturally in their diet. Cholesterol was then found in their arteries but also in their tendons and connective tissue. This finding led to the assumption that foods rich in cholesterol caused heart disease.

      2) The Seven Country Study by Ancel Keys in the late 1950′s, showed an apparent link between saturated fat consumption and the incidence of Heart disease. Ancel Keys showed, on his now infamous graph that the seven countries, all which had a diet rich in cholesterol also exhibited high levels of heart disease. However he had actually studied 22 countries, but the other 15 countries were not included as they had failed to support his hypothesis. They either had High cholesterol diets but a low incidence of heart disease, like Holland or low cholesterol diets and a high incidence of heart disease such as Chile. This fraudulent omission was not published at the time.

      The Lipid Hypothesis hit the mainstream media in the 1980′s. It was based on the assumption that a diet rich in Cholesterol was the cause of heart Disease.

      Once people bought into the idea of a Low Fat Diet, they avoided saturated fats. Butter, eggs and fatty meats were demonised. The food industry jumped on the band wagon. Trans and vegetable fats were offered as a healthy alternative to butter. Low fat products were flavoured with sugar and high fructose corn syrup and Healthy Whole Grains and highly processed foods became much more commonplace in our diet.

      Even fruit and vegetables were offered in forms that were far removed from their natural state. We sprayed them with ever increasingly toxic pesticides and grew them in increasingly barren soil. They lacked the nutrient content of the vegetables our ancestors ate and then we processed them.

      At the same time Wheat was being hybridised to produce the Dwarf wheat we now all eat. The same wheat that is added to nearly all processed foods.

      The famine issues facing many areas of the third world hugely benefitted from the new modern wheat crop that gave all the farmers a high yield of hardy pest resistant wheat with 6 1/2 times more chromosomes than humans. The gluten in the wheat had been altered to such an extent, that it is considerably toxic. Gluten is a protein that no human can digest. We do not have a digestive system to cope with this hybridised version of wheat, unrecognisable from the early wheat of biblical times. It is so nutrient poor that by law it has to be fortified with vitamins. Even ruminants that have evolved to digest plants cannot digest it. Grain fed cattle get very sick if fed it for more than a few months prior to slaughter. And any cattle farmer knows that a cow is fed grains to fatten it up. Grains are known to lead to weight gain in all animals and yet the Government insist they are healthy!

      Grains are the seeds of wheat. All seeds have evolved to survive to grow into a new plant. Plants have many ways of surviving. Some have are attached to edible fruits, like strawberries, which are then passed intact out of the body in a ready made bed of moist manure and able to grow anew.

      All grains (whole or refined) have a higher glycemic index than pure white sugar. This leads to a spike in blood glucose levels which is hazardous. We then secret insulin ( a fat storage hormone) to remove the sugar from the blood and store it as fat. The presence of insulin in our blood also suppresses leptin receptors in the brain that would normally signal satiety. So we store ever increasingly large amounts of glucose as fat while not realising that we are full. And so we continue to crave carbohydrates.

      Grains contain gluten. Gluten comes from the Latin word meaning glue. It is used to bind books. It contains the same double sulphur bonds found in hair and rubber that ensures that they don’t easily break down. Gluten from rice was used to cement the Great Wall of China.

      It also has a morphine like effect on our brain that makes it extremely addictive, which encourages our over consumption.

      The alarming health implication associated with eating grains is that they inflame our gut lining, causing intestinal permeability. This leads us to suffer with scores of auto immune diseases where our bodies tissues are attacked by an immune system overwhelmed by toxins and complex proteins that are leaking into our blood stream. The over excited antibodies then silently attack our brain or our thyroid or our cartilage or our skin or any other tissue until decades later we exhibited the signs and symptoms of a diagnosable condition such as Multiple Sclerosis. Alzheimer’s, Hypothyroidism, or Arthritis which are amongst as many as 200 known chronic, degenerative human illnesses that may be linked to auto immunity.

      Food producers add grains and MSG (which is also addictive) into most processed foods increasing the alarming levels of obesity and ensuring the ever shocking incidence of hundreds of chronic illnesses unique to humans. Animals left to eat naturally in the wild do not suffer like we do. Even zoo keepers recognise that the animals they look after shouldn’t eat our food as it will make them ill.

      As Barry Groves once said

      “Humans are the only mammals clever enough to make their own food and the only ones stupid enough to eat it.”

      • In reply to #6 by maria4freethinking:

        In reply to #4 by mr_DNA:

        I admit to being a bit sceptical about this as a major cause of obesity in the general population.
        People have been eating carbs for a long time but the huge surge in obesity has only occurred in a relatively short time. There must be another factor at work in addition to…

        tl/dr

        Your central thesis rests on this: because we were told to eat low fat, we 100% followed that. That is a faulty assumption. You haven’t demonstrated that American actually follow that rule.

        I would also suggest that there is ample scientific advice that shows saturated fat causes heart disease.

        I wonder if you pulled all this from a pro-Paleo Diet web site.

  4. In reply to System Marked Down

    Your central thesis rests on this: because we were told to eat low fat, we 100% followed that. That is a faulty assumption. You haven’t demonstrated that American actually follow that rule.

    I would also suggest that there is ample scientific advice that shows saturated fat causes heart disease.

    I wonder if you pulled all this from a pro-Paleo Diet web site.

    In Reply

    I am a 54 yr old nurse, who has been suffering with an increasing number of auto immune conditions and struggling with weight gain. I watched my sister and my parents die young from many complex medical problems.

    Then on 30th March 2013, I listened to a talk on Richard Dawkins website by Gary Taubes. I wanted to lose weight for my daughters wedding so I decided to try and cut down my carbs. In four months I lost 36 lbs and was lighter than I have been my whole adult life and I felt so much healthier. But as I continued to research nutrition, I listened to hundreds of hours of lectures and interviews by scores and scores of experts in their fields of medicine and nutrition, from Weston A Price foundation, Dr David Perlmutter, Dr Tom O’Bryan, to Dr William Davies. Also countless Pod cast interviews from Underground Wellness and Jimmy Moore led my interest to quickly move from weight loss to health.

    Every word That I wrote was mine, apart from my quote from Barry Groves. Not a single word was pulled from anywhere. I have never been on a single Paleo website, not because they don’t have a lot of healthy nutritional ideas but because I’m more interested in what the Physicians who are in clinical practice are saying. Try listening to Dr Mary Vernon ‘Low Carbs Explained’ on you tube.

    Your suggestion that my central thesis rests on Americans following a 100% low fat diet, is to miss my point entirely.

    The diet and our environment in America and other western countries that are eating similar foods and exposed to similar environmental toxins has numerous problems.

    It’s not just the original Low Fat Dietary advice, that has caused our problems, but also the indigestible hybridised wheat and other grains that cause intestinal permeability and complex auto immune diseases. It’s also trans fats, mono sodium glutamate, artificial sweeteners, high fructose corn syrup, highly processed foods, pasteurised milk, crops drenched in pesticides, sterile agricultural land, over use of antibiotics, cruel animal husbandry that ensures mass produced meat is nutritionally deficient, fish farms, toxic chemicals that are in virtually every household cleaning product and toiletry and cosmetic item we touch not to mention air and water pollution.

    It cannot have escaped your notice that in the space of just one hundred years, the incidence of Cardiovascular Disease has risen from 1 in 100 people, to 1 in 3 people in America.

    It’s easy to be cynical but these claims are backed by a huge amount of peer reviewed published scientific papers. Just put any of the above words in pubmed.gov and you can see thousands of evidence based research articles. The science is out there for anyone to see.

    I’d like to see the actual science that proves that a low fat diet is beneficial to humans or that saturated fat causes heart disease. Even if high Cholesterol was present in everyone suffering from Cardiac disease, it is only be a correlation and not a cause.

    The science most people get to hear about is presented in summarised Abstracts taken from studies paid for by Big Pharma. They pay scientists big money to prove pre determined hypotheses. It’s hard to get Research posts to If you want to do independent studies. So many research institutes are funded by Companies with a conflict of Interests. You have to ask who gains when we are all led like lemmings down the path of Statins for all. Maybe the Drug Companies who are making Billions trying to convince us that Cholesterol causes heart disease, instead of admitting that 50% of people diagnosed with Cardiac disease do not have ‘high cholesterol’. Maybe the high levels of oxidised LDL Cholesterol that blocks coronary arteries, aren’t the cause, but merely a sign that there is a disease process in play with a much more complex set of toxic factors leading to the inflammatory state that is Coronary Artery Disease.

    Maybe instead of so easily dismissing this information, you should consider doing some research of your own.

  5. In support of the contribution from Maria4freethinking:

    There’s a precedent in public health research involving exclusive reliance on inductive reasoning via statistical techniques of correlation. Most famous example being the successful linking of tobacco as causing lung cancer and cardiovascular disease. Research employing similar techniques implicating dietary saturated fat as being the cause of heart disease is very much nothing like as clear as in the case of tobacco.

    Unfortunately for many researchers these correlation techniques are the only real tools they’ve got. All that’s needed is a PC , a phone, and a desk. There’s much less funding for anything else like expensive lab equipment and technically sophisticated physiology experiments. With only one tool then all problems end up looking like a nail.

    Generally it’s difficult to really pin something down just via correlations. Tobacco was a major breakthrough, but was relatively easy in comparison with saturated fat because it was possible to define large and relatively similar populations which varied in crucial parameters. Like groups of people who had smoked cigarettes for a long time and then stopped, or people who had not smoked and then started. And people who smoked only little or people who smoked only a lot. It’s very difficult to address similar populations to indicate a reliable dose-dependent response in connection with saturated fats – which our bodies are actually made of to some extent, and which is more or less a consistent and unavoidable component of normal human food for most people. This situation is very different with the trans fats, another very stable industrial form of fat which has been an element in human diets only very recently in response to attempts to supplant saturated fats. (Saturated fats being relatively stable and useful in processed foods to extend shelf life and enable centralised production for scale economies in the food industry).

    A confounding factor with saturated dietary fats is that they are not independent of other macronutrients. Especially in processed foods which incorporate diabolically addictive blends of stable fats (saturated), sugars (mostly fructose – being sweetest, also preservative), and salt (also a preservative). Plus of course added preservatives: probably fat, sugar, and salt – though described in technical jargon, in addition to the other fat, sugar, and salt, in the nutritional analysis for consumers. Then there’s the flavouring: being essentially fat, sugar, salt also. Typically there will be a complex breakdown showing every different kind of sugar molecule as a separate percentage – all the better to conceal what’s really in the food. The healthiest nutrients probably being the food colouring and the indigestible fibre of the cellulose in the cardboard box these products are sold in. Or possibly it’s the added caffeine. Even the added vitamins and anti-oxidants currently used to fortify these ‘health’ ‘foods’ have recently been established as carcinogenic.

    We probably have the tobacco industry to thank for the saturated fat & cholesterol theory of heart disease. From this industry’s perspective funding any research that took the focus off tobacco as the cause of the massive post war incidence of decades delayed heart disease (perhaps thanks to free ciggies for the WW2 solders) was a fortuitous and lucrative investment. Now that the tobacco industry has pretty much morphed into the processed foods industry there may be an aspect of history repeating itself.

    The major problem with saturated fats as a hypothetical cause of heart disease is similar to the epidemiological link with tobacco consumption. The tobacco industry long claimed that the specific cause of lung cancer and cardiovascular disease had not been identified. And that correlation doesn’t imply causation – even if it is a valid justification for where to start looking for actual causes. Maybe smoking actually helped alleviate unpleasant symptoms of lung cancer etc, so that most people with lung cancer ended up smoking, even though the cancer was attributable to other unknown causes? This argument was well met by further creative correlations. And by establishing actual model mechanisms by which tobacco caused lung cancer and heart disease. Though obviously tobacco was never the exclusive cause of these diseases. It’s a shame those mechanisms are now over-looked, because they are probably the same mechanisms by which other ingested molecules cause similar damage to arterial linings.

    Despite the prolonged fashion of asserting that saturated fat causes disease I’m not aware that there yet exists a convincing model of how normal levels of dietary saturated fats actually contribute to cardiovascular disease. (Maybe I’m wrong on this, it’s a moving target so please let me know!) In contrast to mere assertion there is a very plausible model for how other ‘normal’ dietary components do contribute to cardiovascular and many other degenerative non-communicable diseases. These involve dietary components that tend to be overlooked in correlations involving saturated fat. i.e. It’s a case of obtaining subtle statistical evidence to support a preferred theory, but overlooking other variables that also explain the variance, perhaps much more strongly.

    The source of research funding in public health seems to be what governs the direction of the research, which is not necessarily where the evidence leads. There’s increasing cause for disquiet about what’s been going on with some areas of research in the health sector. Much of this funding is via government, which tend to be highly prone to industry lobbying and undisclosed conflicts of interest.

    A very good example of this conflict of interest is Rory Robertson’s recent expose of ‘The Australian Paradox’: a peer-reviewed and highly cited and internationally influential paper (arguing against junk food taxes) that demonstrates that obesity in Australia has absolutely nothing at all to do with sugar consumption – but that this relationship only holds in Australia. Where a major university happens to be heavily dependent on revenue from the global processed foods industry associated with globally licensing its ‘low glycaemic index’ certification to processed foods. The glycaemic index of processed food products being lowered (made more ‘healthy’) simply by adding large amounts of sugar – i.e. making the product lower in percentage fat.

    Other plausible dietary disease models being that grasses have evolved anti-mammalian defensive proteins which compromise gut function in predators (for which many browsing herbivores have evolved to tolerate). High starch diets (typically combining saturated fats and salt as in most processed foods) based on grass products, e.g. wheat seeds, may be a serious problem for many people.

    There’s also the random endogenous glycating impact of chronic tissue exposure to elevated blood sugar (as occurs most acutely in the glucose intolerant – being the point of the linked article) and which is also caused by fructose, alcohol, tobacco products, and some fats (though possibly to a much more limited extent). The major effect is caused by glucose, simply because that’s the highest volume and most acute source of chronic exposure, via high starch diets.

    People who exercise regularly and who sleep normally just don’t eat huge amounts of saturated fats or starches in their normal diets. Unless of course precise proportions of these macronutrients are assembled into products to trigger the bliss factor – an evolutionary accident but which is very heavily exploited by food manufacturers.

    Regarding obesity:

    In addition to the basic evolutionary advantages of storing long-term food energy, obesity is also the human body’s way of rapidly extracting sugar-related glycating molecules from the bloodstream as quickly as possible. This glycation mitigation doesn’t occur very well in insulin insensitive people. But glycation mitigation does occur most effectively in the young and physically active, because youth implies growth hormone secretion which stimulates substantial cellular repair and growth activity, which in turn burns energy prodigiously, which in turn depletes glycogen reservoirs. Available glycogen reservoirs (in the muscle cells), provide a substantial sink for excess dietary blood glucose to be safely sequestered to prevent glycation damage to structural and functional proteins. It is this damage that probably contributes to the NCDs of the prevailing NCD epidemic.

    It was a study into why children who watched too much TV ended up with poor eyesight that identified some of these easily observable glycation effects on retinal arteries. Being that watching TV was related to inactivity, which was related to nutrition. Specifically significantly more sugar intake via cordials, sports drinks, soft drinks, fruit juice etc. compared to active and less TV-oriented kids. Though this is a work in process. Last I heard they were stalled for funding. (Maybe few are willing to fund research that doesn’t have optimistic implications for pharmaceutical sales.)

    There are very good models of how cardiovascular disease occurs in this way: via glycation impact and consequential inflammation. The correlations are equally, if not more, valid for sugar exposure than for saturated fat exposure. The advantage is strongly towards the dietary sugars exposure hypothesis (i.e. mitigated by low carb diets) because there is also an actual testable theory and known mechanisms for how the physical cellular damage occurs.

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