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Anyone who’s ever struggled with weight loss issues has probably questioned their metabolism, but what nutritionists have known for some time now is that, when it comes to diet and fitness, what works for one person won’t always work for another.

“Just like we all enjoy different styles in fashion and different music and movies, we also intuitively understand, on a very deep level, that one person’s food is another person’s poison,” says Uma Ghosh, a Dubai-based health coach. “As a health coach I strongly believe we are all bio-individuals. That means there is no one diet fits all. General health recommendations don’t always work, and each person needs to figure out what works for them.”

American biochemist Roger Williams, better known for isolating folate and discovering the vitamin B6, first floated that concept in a book called Biochemical Individuality in the 50s, arguing that dietary and other needs are determined by our genetics, and vary from person to person. That explains allergies and food intolerances, but although there are now DNA tests offering tailormade diets, scientists at Stanford University showed in a study last year that genes alone won’t predict why different people process foods differently.

But no, metabolism isn’t all genetics…

That has been proved yet again following the largest study of its kind. Even identical twins often have different responses to the same foods, researchers showed at the American Society of Nutrition’s Annual Conference this month [June 8-11]. The study, led by Tim Spector, Professor of Genetic Epidemiology at King’s College London and author of The Diet Myth, followed 1,100 UK and US adults — 60 per cent of whom were twins — for a period of two weeks and examined blood markers such as blood sugar, insulin and triglycerides. “Our results surprisingly show that we are all different in our response to such a basic input as food. It was a real shock to see that even identical twins have such different responses,” Professor Spector said in a media statement.

Identical twins who share all their genes and most of their environment often had different responses to identical foods. The study also finds that identical twins shared just 37 per cent of their gut microbes — only slightly higher than the 35 per cent shared between two unrelated individuals. The trillions of microbes living in our digestive systems play an important role in digestion and assimilation, and an imbalance in their numbers, has been associated with chronic illnesses such as diabetes and liver disease.

Individuals in the study also showed a wide variation in blood responses to the same meals — and displayed large differences in responses depending on the time of the day they were eaten. Genetic factors only partly explain the discrepancy — up to about 50 per cent for glucose, less than 30 per cent for insulin and under 20 per cent for triglycerides.

So yes, you are what you eat — and more…

Surprisingly, the composition of a meal in terms of fat, proteins or carbohydrates, explained less than 40 per cent of an individual’s response. Dr Andrew Chan, Professor of Medicine at Harvard Medical School and a gastroenterologist at Massachusetts General Hospital, who was also involved with the study, said, “It is reassuring that our genetic makeup only partially explains how our bodies respond to food. This underscores that our metabolism is not fixed — we have the power to change it. One exciting avenue is to tailor our diets to the bacteria in our gut that helps us metabolise nutrients.”

Predisposed doesn’t mean predestined

- Dr Remy Shanker, a UAE-based doctor and nutritionist

The study chimes with other research indicating that many other factors play a role in the way we process food, from fitness and stress to social bonds and the quantity and quality of sleep.

“Predisposed doesn’t mean predestined,” agrees Dr Remy Shanker, a UAE-based doctor and nutritionist. “Ninety per cent of an individual’s current health status is controlled by the environment in which we bathe our genes in. One no longer needs to sit back and accept these are the cards they have been dealt. While genetics loads the gun, one’s lifestyle is what pulls the trigger!”

The broad parameters for nutritional health are widely known, and Dr Shanker recommends fixing these root causes first. Eat a healthy diet with the different macronutrients in moderation (a mix of proteins, carbohydrates and good fats, principally from whole foods such as vegetables, fruit and lean meats), increase your daily fibre intake (vegetables, legumes, whole grains), cut out processed foods and anything containing hydrogenated vegetable oil, incorporate omega 3 fatty acids into your diet, and so on.

How to find the right diet for you

Beyond that, it’s important to monitor how you react to different foods, and how you feel. “Understanding your body’s cues such as bloating, excessive gas, irregular bowel movements, acne breakouts or lethargy, for example, can help you pinpoint causative foods that trigger these symptoms. Tuning in to your body’s signalling system of even when and how you feel hungry can help you reengineer your diet and assimilate or process food differently,” she says.

Dr Shanker suggests keeping a food diary to log your daily intake and track your responses. “Dedicate 48 hours to write down and analyse what you feel, mentally and physically. This can help you realise a life lesson about your own body.”

Start your day with a sugary breakfast cereal and you might notice you’re seeing mood swings and craving more sugar. Alternatively, breakfasting on quality protein and the right amount of fats could keep you energised and satiated until your next meal, while keeping you mentally alert. Or perhaps not. A journal is simply a way of gathering data; a periodic review, as with any other data set, can confirm or negate previous assumptions, while throwing up new correlations.

Logging activity also helps —take the stairs for a week and note how you feel at the end of each day, and at the end of a couple of weeks, and your breathlessness may disappear and you may find your backaches have dimmed considerably.

“You can master your own health without a degree in medicine,” Dr Shanker says. “When you start to pay attention to your body’s cues that’s when you let your own body lead you to longevity.”

So while you may not have an enviable metabolism, there’s no reason why you can’t achieve your dreams — you just haven’t found the right lifestyle plan yet!