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The same meal plans don’t even work for identical twins, study finds

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For everyone desperately seeking slimming advice from Instagram foodie influencers: don’t bother. 

It’s not much use trying to follow your family’s advice on what they eat to stay slim, either – even if you’re an identical twin.

Even sticking to standard dietary guidelines – cutting down on fats and carbs, and meticulously counting calories – is something of a shot in the dark at what your body really needs.

According to groundbreaking new research, the nutrients on our plates have very little influence on our responses to food, and our genes only determine about 50 percent of our reactions.

What’s more, while some of us would do well to cut down on fats, others would be better off watching their carbs, and some needn’t bother at all.

In fact, the most important factors that determine whether we will put on weight, develop diabetes, or suffer indigestion are environmental – including stress, sleeping patterns, exercise, and what bacteria live in our guts.

The study, the latest in a near 30-year endeavor by Kings College London epidemiologist Tim Spector, is one of the strongest endorsements to date that personalized diets are key if we want to truly control a person’s risks of obesity and other diet-related diseases.

Our gut bacteria is influenced by a myriad of things, and those things all influence our health dramatically. It means someone else’s diet plan may not work for you (file image)

Dubbed ‘Predict’, the project is the largest ever to analyze what influences individual responses to nutrients, involving 700 identical twins, another 300 Brits, and 100 Americans. 

The full findings have yet to be published, but the team shared some details at a conference on Monday, shattering many of our firmly-held beliefs about genes and food in the process.

Working with a team at Harvard Medical School, Spector, the founder of the British Gut project and Twins UK (both exploring the same question), found diet needs to be highly personalized if it’s to have an effect on how we look and feel. 

Over two weeks, they studied how each of their 1,100 participants’ blood levels reacted after every meal. They compared this data with a record of each person’s exercise habits, sleeping patterns, body fat, and sampled their gut microbiota.

One case study summed it up: one twin experience huge spikes of fatty acid (triglyceride) in their blood every time they ate chips. Those spikes were a staggering six times higher than their twin, whose body was largely unfazed by the snack.  

This is hardly the first suggestion that our gut bacteria is influenced by a myriad of things, and those things all influence our health dramatically. 

The American Gut Project, a parallel to Spector’s work, published data in 2016 showing 800 people on popular diets had hugely varied responses to the same food.

And a study in Israel made headlines in 2015 finding that some people are better off with rice and ice cream rather than a salad, and vice versa.

But Spector’s focus on twins shows clearer than ever that we need to take broader look at every aspect of a person’s lifestyle to understand their dietary needs.

Only then will we be able to get a powerful handle on the rising rates of obesity, diabetes, digestive disorders, and colorectal cancers. 

There are moves in that direction.  

Dr Rob Knight, co-founder of the American Gut Project, said his team is working on many ‘science fiction’ ideas to revolutionize how we understand our personal gut health: 

  • A ‘smart toilet’ that examines your fecal matter and offers a live report of ‘how you’re doing’
  • A ‘smart mirror’ that gives an analysis of your breath when you breathe on it, much like the cystic fibrosis breath tests available
  • An app synced with your smart toilet that could scan grocery items while you’re shopping, and can tell you what you should buy to eat

And Emulate, Inc, a biotech start-up, has successfully developed a ‘gut on a chip’ – using a sample of DNA to perfectly replicate a person’s gut microbiota inside a tiny piece of plastic. 

Dr Geraldine Hamilton, Emulate’s founder, suggests that we may all one day carry our chips with us – with one for our heart, one for our kidney, one for our lungs, brains, guts etc – to a doctor’s appointment, to test new diets or medications on the chip and better understand how our bodies might respond. 

It’s complicated by the fact that our gut microbiota is changing every second of every day. The way you’re born – whether by natural birth or a C-section – has a huge impact on your gut microbiota. What you ate this morning, how much you slept last night, and how many late-night emails you had to field will all affect how you metabolize that burrito. 

For now, lacking more specific tools, Spector, cautions that we shouldn’t flippantly dismiss dietary guidelines.

It is still a good idea to prioritize veg over red meat, and water over a milkshake.


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