Go Hybrid. Humans are designed to run on both fat and carbs for fuel. So use them both

By Jerome Burne

The Hybrid Diet by Jerome Burne and Patrick Holford (Piatkus £16.99)

If you are not confused about what you should be eating to stay healthy, you haven’t been paying attention. I’m a medical journalist so I have to pay attention and my friend Patrick Holford is a nutritionist and has been writing books about healthy eating and advising clients for years, so he also keeps up to date.

Several months ago, we both noticed something very odd. Humans have been eating animal fats and dairy as well as the carbohydrates from fruit, vegetables and grains for thousands of years and yet we were in the middle of a standoff between two camps, each championing a different food type – or macronutrient to use the technical term.

One side was saying fat is damaging and should be kept to a minimum and the other was advocating dropping your carbohydrates very low and replacing them with fats both animal and vegetable. Each accused the other of having a diet that was unhealthy and lacked evidence that it was safe or effective.

Later this month, our book, called The Hybrid Diet, comes out which we believe contains a blueprint for a peace treaty; a way of eating that allows the benefits of both, plus a twist, But before I explain why it makes sense and what it involves, I’m taking you on a lightning tour of where we are now and why some sort of peace and reconciliation is badly needed.

Counter-reformation targets saturated fat

You may have recently picked up on the fact that fat – saturated in particular – for so long the demon in your diet, has been rehabilitated for lack of evidence that it causes health problems.

For decades, repeated, large-scale trials replacing saturated fat with vegetable fats had failed to find any reduction in the risk of heart disease. What’s more, any evidence that fat made you fat had been missing when the low-fat guidelines were first produced in the 1970s. References for these very broad claims are in the book.

That re-think had been attracting a lot of interest from endurance athletes, anyone interested in weight loss and from diabetics, fed up with seeing no improvement on the official low-fat high-carb diet. Then the blowback began, especially from an increasingly assertive vegan lobby, which was firmly and ideologically opposed to eating animals or their fat in any form.

Adam and Eve were Vegans

The movement, interestingly, is heavily backed by the American millenarian sect The Church of the Seventh Day Adventists, which believes that Jesus is returning anytime soon. One explanation for the religious link to their food choice is their belief that a vegan diet was eaten in the Garden of Eden, so it makes sense to eat it here, as believers could be off back there at any moment.

For support, those favouring an animal-free diet point to studies that tracked people for years who said they didn’t eat much if any animal products and found they were often healthier than those who favoured bacon and steak etc.

There’s now a vigorous debate going on between no animal product vegans and supporters of the ketogenic, high fat low carbohydrate diet that is designed to involve eating a lot of fat. Ketogenic supporters describe the vegan diet as likely to be deficient in various nutrients and exposing you to the risks that come with a diet high in refined carbohydrates.

The vegans have big money on their side – not only the 7th Day Adventists but also a Swedish billionaire who is on a mission to reverse global warming and save the planet as set out in a recent paper in the Lancet by a group calling themselves EAT Lancet.

Those advocating the ketogenic diet (conflict of interest declaration here: I think the ketogenic diet is the most interesting and promising approach to eating in forty years) don’t have anything like the dollars behind them but they do have some serious, independent researchers who have very effectively dismantled the case for low fat and are gaining converts to the health benefits of the ketogenic approach. Most impressive results so far involve diabetes – reversing the disease and being able to reduce or stop taking the drugs. (More details and references in the book).

In fact, we are made to use both fuels

So, is meat a killer rather than fat? And if fat has twice the calories of carbs why doesn’t a lot of olive oil pile on more pounds than several croissants? Won’t cheese block your arteries? Plenty of causes for confusion.

What we felt was missing from the standoff was an appreciation that humans are hybrids; we are designed by evolution to run on two sorts of fuel – blood glucose from carbohydrates and ketones made from fat. This means that neither of them is likely to deposit you in A&E one day if you eat mostly natural versions of any food and largely avoid products of the food industry

Nobody disputes that glucose is a fuel needed by the brain, but ketones – small energy units made from fat in the liver – are more unfamiliar. We have had sixty years of carbohydrate abundance, just look along supermarket food aisles or go into a coffee shop and see how many products are carbohydrate-based. This has allowed ketones to fade into obscurity. Dietitians, who are supposed to understand physiology, regularly warn that making lots of them can be dangerous.

The truth is that not being able to make ketones would be fatal if you lived somewhere that food shortages and famines were common. The ketone system evolved to provide an alternative fuel to glucose for the brain. Our bodies don’t have more than a few days’ worth of glucose supplies. When that runs out, your brain starts to shut down.

Low carbs: unlocks the fat stores and takes out the garbage

What the low carb diet does is to send a message to your food sensors saying: ‘There’s a famine starting up out there, better begin conserving resources and repairing.’ This is a state known as ketosis. First fat is released from fat stores in popular weight-loss-target areas such as around the tummy.

Then comes a cascade of metabolic changes. A program called autophagy, which provides a clean-up service for every cell, is turned on, while one called mTOR, which directs the use of energy for growth, is turned off. Ketosis also makes intermittent fasting easier and more effective.

But what about the other side of the hybrid model, what we are calling in the book ‘slow carbs’? This is based around Patrick’s years of experience with the low Glycaemic Load (GL) diet. In this part you continue eating complex carbohydrates found in various fruits and vegetables which gradually release glucose into the bloodstream, avoiding the damaging glucose and insulin spikes common on a low-fat diet. You just eat just the vegetables or include meat and dairy. There’s no need to restrict fat.

Patrick’s experience is that this slow carb approach – which is similar to the one now being used by many diabetics to control their condition – is just as effective as ketosis for weight loss and for coming off diabetes drugs. Its other advantage is that you don’t have to be quite as strict over lowering carbs. There is no need to give up heavy but delicious carb foods such as rice or bread or potatoes.

The secret is switching between the two

The ketogenic diet can be challenging and individual responses to it vary. It is probably most useful if you have a specific metabolic condition when the large drop in insulin and glucose is very beneficial, or for a short clean up. The hybrid diet allows you to alternate between a more relaxed and more demanding way of eating that packs a bigger metabolic punch. This is a cycle that genetically our bodies are very familiar with.

By switching between a high fat phase – which damps down mTOR and growth and turns on autophagy – and a slow carb phase – which turns mTOR back on promoting healthy growth and repair – you get the best of both worlds and allow insulin, IGF-1 (insulin growth factor 1) and mTOR to orchestrate all of the growth processes you need to thrive.

 The Hybrid Diet is a perfect fit for the lifestyle healthy eating approach being promoted by the ANH (Alliance for Natural Heath), among others. Here is their review of the Hybrid Diet.

The idea of the ANH’s ‘Blueprint’ is to pay attention to your body’s ‘terrain’ – the interaction of the main systems such as circulation, blood sugar control, the smooth working of your guts, detoxification, the immune system and your hormones.

 This is gradually emerging as a more logical way of staying healthy and preventing disease as it’s rooted in the way our bodies have evolved. The current drug-based approach to prevention aims to put as many people as possible on a narrow range of drugs that target a few random biomarkers such as cholesterol, blood pressure and blood glucose.

A way to avoid rattling with pills as you get older

Some of the targets make sense but the drugs come with a nasty range of side effects and, out of a hundred or more people taking one of the drugs, just one may benefit. By the time you are a pensioner you are likely to be a victim of polypharmacy, that is taking a dozen or more drugs to stop you getting sick in combinations that have never been tested and are very likely to be making you feel unwell.

In contrast to this, the two arms of the Hybrid Diet can benefit many of the systems that make up your terrain, the ecological system that is keeping you healthy. It’s certainly possible to get enough of the vegetables your microbiome needs to flourish when you are in ketosis but its easier when you are eating slow carbs. A toxic clean-up comes with the autophagy that ketosis triggers. Then when you switch back to slow carbs, mTOR ramps up and you will be building not just muscles but also replacing immune cells.

The ketogenic diet can have a dramatic effect on diabetes because significantly dropping carbohydrates immediately brings down glucose and insulin levels, which will have crept up too high. The same reasoning suggests the diet could also protect against heart disease. Raised glucose and insulin puts on weight and damages the lining of the arteries; the ketogenic diet can reverse both. The idea that fat makes you fat no longer carries much weight.

A diet that can both heal and keep you well

Another disorder that has a messed-up metabolism is cancer and increasingly it is looking as though patients could benefit from the way ketosis will cut back on the availability of one of cancer’s main fuels – glucose – as well as from anti-cancer changes ketones can produce in cancer cells. Details of all these can be found in the book,

But if you aren’t battling with a chronic metabolic disorder or trying to lose weight, or an endurance athlete looking to use your fat stores for energy, then you might prefer to avoid the more disciplined eating that comes with ketosis and be rather more relaxed on slow carbs. One possible pattern would be to stay on slow carbs for most of the time, switching to the ketogenic option for a week every few months. This would allow you to regularly activate some of those healthy metabolic changes that can help to keep your terrain in good shape.


Patrick will be presenting seminars on the Hybrid Diet from March 18th to April 10th in Daventry, Manchester, Dublin, Belfast, Sligo, Tralee, Cork, Kilkenny, Cardiff, Marlow, Richmond, London (Parsons Green, Piccadilly and Kings Cross) – details at hybriddiet.co.uk. Click on the icon saying “Seminars and Retreats”

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Jerome Burne

Jerome Burne

Jerome Burne is the editor of HealthInsightUK. He is an award-winning journalist who has been specialising in medicine and health for the last 10 years and now works mainly for the Daily Mail. His most recent book “10 Secrets of Healthy Ageing” was written with nutritionist Patrick Holford. He blogs at “Body of Evidence” – jeromeburne.com. 2015: Finalist for 'Blogger of the Year' award from Medical Journalists' Association.

11 Comments

  • “…our book, called The Hybrid Diet,[insert promo page link]…”

    Tee hee.

    Nice article, though, and very balanced. Like the diet it recommends.

    I think the issue is slightly confused by the fact that so very many modern Westerners are extremely overweight and want to lose weight. That seems to be done more easily with very limited carbs, although YMMV.

    I have been losing some weight – finally, after many frustrated attempts – by a combination of 2-week fasts and low-carb eating in between. (Shout out to Dr Jason Fung and others).

    But it wouldn’t have been nbecessary if I hadn’t already been seriously overweight by the age of 14, despite being a keen middle and long distance runner.

    • Editorial

      Yes link to promo page instruction did survive on line for too long. Gone now.
      What’s exciting for me about HD is that opens up a lot of unknowns about metabolism and genetic research plus microbiome data will identify lots more individual differences. While idea of one-diet-fits-all is dead, we do feel that HD offers many more options to accomodate such variation.

  • An interesting bridge between two extremes. I look forward to reading the book

  • “The ketone system evolved to provide an alternative fuel to glucose for the brain. Our bodies don’t have more than a few days’ worth of glucose supplies. When that runs out, your brain starts to shut down.”

    I realise that this is a light touch overview, but this seems a little misleading to me.

    As far as I know the brain requires glucose to feed some areas because ketones cannot pass the blood/brain barrier in some cases.

    So the brain might have some fuzzy time (often called carb flu) as it adapts, but after that the brain should be fine and the body will manufacture enough glucose from protein and fat to power the brain and some other metabolic functions which are glucose dependant. Many other metabolic functions (not just the brain) which prefer the easy energy of glucose can switch to burning ketones if required.

    This is why people can survive for weeks (months?) in an open boat with nothing but water. As you say, alternative strategies for the body in lean times.

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      My undestanding is that BBB not a problem for ketones – ‘cannot pass….in some cases’. When.where why?
      Also fat needs to be turned into ketones to be used as fuel by the brain and deriving enough glucose from protein would mean losing an awful lot of muscle mass??

  • Good article. Back in the 80′s Covert Bailey, Author of ‘Fit or Fat’, was pitching the benefits of aerobic exercise as a means to regain the ability to control one’s weight. He explained to his audiences that, at rest, muscle tissue derives 60% to 70% of its energy needs from fat and the remainder from glucose. During aerobic exercise, muscles burn up to 80% fat. Of all the nutrition authors I’ve read, Bailey is the only one to point this out.

    Bailey also taught that aerobic exercise increases both glycogen storage capacity and the rate of removal of glucose from the bloodstream. This has implications for blood sugar control.

    But aerobic exercise is not the only weight control option. Lowering arachidonic acid intake can also be helpful. How does that work? It has to do with appetite control. The name of the game is to lose weight and keep it off without experiencing discomfort. Excessive arachidonic acid intake tends to hyperactivate the endocannabinoid system deranging the appetite. For example, “The endocannabinoid system is implicated in both homeostatic and hedonic food intakes, with activation of the system resulting in an increase in hunger. Specifically, anandamide (AEA) and 2-arachidonoyl glycerol (2-AG), which are derivatives of arachidonic acid (AA), bind to the main two receptors, cannabinoid receptor 1 (CB1) and cannabinoid receptor 2 (CB2), leading to activation of pathways to initiate food intake in the limbic system, hypothalamus and hindbrain. https://www.hindawi.com/journals/ije/2013/361895/

    How does one avoid consuming too much arachidonic acid? By moderating meat intake. Excerpt from a 1992 review by Olaf Adam:

    “Within the last 50 years, changing nutritional habits in Western communities led to a fourfold increase in the supply of dietary arachidonic acid (AA), provoked by the same increase in the consumption of meat and meat products. A low oxidation rate and a high affinity uptake system result in the accumulation of AA in cell lipids. Clinical experiments with AA supplements showed the efficient enrichment of AA in plasma lipids and a consecutively exaggerated production of eicosanoids. Several diseases observed with increasing incidence in Western communities are characterized by enhanced eicosanoid biosynthesis, and inhibitors of eicosanoid production have been effective in the treatment of these diseases, e.g., aspirin in the prevention of atherosclerosis, nonsteroidal antiinflammatory drugs in the treatment of arthritis, and glucocorticoids in the treatment of allergic and immunologic diseases.” https://link.springer.com/article/10.1007/BF00180737

    Arachidonic acid is also formed from it’s shorter chain precursor linoleic acid. High linoleic acid intake is problematic for certain population groups. “Those whose ancestry derives from vegetarians are more likely to carry genetics that more rapidly metabolise plant fatty acids,” said Tom Brenna, Professor of Human Nutrition at Cornell. “In such individuals, vegetable oils will be converted to the more pro-inflammatory arachidonic acid, increasing the risk for chronic inflammation that is implicated in the development of heart disease, and exacerbates cancer.” https://www.telegraph.co.uk/news/2016/03/29/long-term-vegetarian-diet-changes-human-dna-raising-risk-of-canc/?WT.mc_id=tmg_share_tw

    So even with low meat intake, vegans and vegetarians will be prone to obesity if they do not restrict linoleic acid intake. Rather than go on about this, I recommend this book chapter. Read it in its entirety because it explains a lot. https://www.intechopen.com/books/glucose-tolerance/importance-of-dietary-fatty-acid-profile-and-experimental-conditions-in-the-obese-insulin-resistant-

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      Thanks David – So it is arachidonic acid that give you the munchies. Interesting. Risks of meat certainly disputed area. Are studies showing a link but critics point out they are observational and processed meat consumption muddies the water. Not that i’m an expert (only a messenger) but was intrigued by point that for some groups plant fattty acids can form inflammatory arrachidonic acids. Issue for vegetarians particularly.
      Hybrid Diet throws up a lot of ongoing disputes. Could be calm space to investigate without an agenda

      • The two most pronounced changes in dietary intake Globally are the increase in meat intake and the increase in culinary oil intake. People love their fried foods. Global obesity expert Barry Popkin singled out meat and vegetable oils several times in a 2003 article published in the Orlando Sentinel. Popkin wrote, “If you go back to those same villages or slum areas today … their diet includes a lot of vegetable oil … In China … Rice and flour intake is down, and animal-source foods such as pork and poultry and fish are way up, and the steepest increase is in the use of edible vegetable oils for cooking … People are eating more diverse and tasty meals; in fact, edible oil is a most-important ingredient in enhancing the texture and taste of dishes … The edible-oil increase is found throughout Asia and Africa and the Middle East as a major source of change.” https://theecologist.org/2014/feb/24/linoleic-acid-overwhelming-evidence-against-healthy-poly-unsaturated-oil

        Arthritis researchers have experimented with reduced meat intake intake. For example: https://link.springer.com/article/10.1007%2Fs00296-002-0234-7

        In metabolic syndrome research, “… study identifies arachidonic acid as an important independent marker of metabolic dysregulation.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2730166/

        I’m still searching for experimental evidence demonstrating weight loss in conjunction with reduced arachidonic intake. In a 2007 paper, lipids researcher Philip Calder said that “…it is important to keep in mind that, just because there is little biological impact of an increase in arachidonic acid intake or status, there may still be significant benefit from a decrease in its intake or status.” https://www.researchgate.net/publication/6133751_Dietary_arachidonic_acid_Harmful_harmless_or_helpful

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          thanks david – always impressed by your extensive and historial knowledge of lipids. Remember you telling me some years ago about somone working on the Indian railways (have i got this right?) called Aseem Malhotra who was doing some radical lipid research (details have faded i’m afraid)

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