Saturday, March 6, 2010

Test your genes and loose the weight?

Do Your Genes Determine Which Diet Means Weight-Loss or General Health Success?
Can nutrition be optimized with respect to your genome?

Commercial genetic tests promising to provide personalized diet recommendations (there were 6 in 2005, not counting companies developing DNA nutri-chips to pinpoint an animal’s nutrition needs) are constantly offered and withdrawn. Interest in genetic testing over the past few years was going down (click on the right figure to see google trends), but continuously published findings cause bursts of interest (click on the right figure to see XRanks by Bing) .
Clearly, genetic variations determine how we absorb, filter, metabolize, store and eliminate nutrients and how these nutrients affect processes in our body. But should we get more vitamin B if our MTR gene carries predisposition to heart disease or have extra calcium and vitamin D if our VDR gene indicates possibly weak bones?
The use of this information may be premature, the gene-vitamin linkages may not be credible, and far inferior to your family health portrait with much higher cost-to-benefit ratio than self-evaluation and self-awareness through personal health management tools.

It Isn't Just What You Eat That Can Kill You, and It Isn't Just Your DNA That Can Save You--It's How They Interact, said a 2005 newsweek article. It is also about other environmental factors, your history of interactions, and microbes you cultivated in your system that determine what food is best for you.

Lactose intolerance, for example, may be derived from genetic tests showing how effective our bodies are in producing the lactase enzyme (the LCT gene). We can determine it in a much cheaper and reliable way, however, by drinking milk and looking at the symptoms. Same about FMO3 variations and trimethylaminuria. A study of lung cancer rates in China found that people at lowest risk were genetically deficient in an enzyme that metabolizes isothiocyanates in cruciferous vegetables, but crucifers don't seem to harm those with a functional enzyme either... except those who gets get intestinal gas from eating them. But this may not be because of the genes, but due to the lack of beneficial gut bacteria.

The weight-loss industry long admitted that one specific diet isn't likely to work for everyone. How do diet programs work? Forget about the ratios of carbs, fiber and protein, the most important factor is to burn off more calories than you're taking in. Behavioral factors rather than macronutrient metabolism are the main influences on weight loss, so it's more about mindful eating versus mindless eating. And here genes come into play again. Satiety mechanisms are complex and involve multiple sensors, operating differently according to underlying genetics. that's why a carb-heavy breakfast can leave you hungry in two hours but keep your neighbor full until noon, while high-protein diet makes you fill fuller.

This week (at the American Heart Association’s Joint 50th Cardiovascular Disease Epidemiology and Prevention – and – Nutrition, Physical Activity and Metabolism conference, being held March 2-5 in San Francisco, CA) Stanford University researchers reported that a genetic test can help people choose which diet works best for them. The study involved 133 overweight women, who lost more weight on a diet that matched their genes - either low-carbohydrate or low-fat. Improvements in clinical measures related to weight loss (e.g., blood triglyceride levels) paralleled the weight loss differences.

The findings are also partially based on an earlier paper, called the A to Z weight-loss study published in the Journal of the American Medical Association in 2007 and a small (100-person) unpublished study by Interleukin Genetics.

More than 6,000 genes may be affecting our weight, including multiple genes determining our taste preferences (e.g., to bitter foods, calcium, garlic or coffee) and behavioral predispositions. Genetic testing along with protein- and metabolomic-based diagnostics would provide invaluable data for understanding ourselves. Data-mining tools for health-related factors will allow integrated and holistic analysis and help to personalize diets, fitness and medical treatments.

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