Scientific studies make it official: for reasons encoded in your DNA, some people really do gain weight more easily and experience more difficulty shedding it, than others. But here's the good news: Another study has shown that people genetically predisposed to weight gain achieve greater benefits from daily exercise than people who don't have to try as hard.
DNA and Genetics
Genes are composed of dioxyribonucleic acid, DNA, a molecule shaped like a spiral ladder present in all of the the body's cells. Arranged along the length of 23 pairs of chromosomes, genes contain encoded hereditary information, determining your appearance and a host of characteristics such as athletic prowess and musical ability, and your predisposition to various health conditions, including obesity. Everyone's DNA is like a fingerprint, unique to that individual.
Weight and 'Thrifty' Genes
The "thrifty gene" theory holds that some people have inherited DNA that helped their ancestors survive times of famine by slowing down fat-burning activity, thereby creating population groups predisposed to obesity. Experiments conducted at the Salk Institute in La Jolla and reported in the December 2010 edition of the journal "Nature," studied the effects of CRTC3, a gene associated with obesity, in two groups of mice fed an identical high-fat diet. Those bred without the gene stayed lean but mice with the gene got fat. A similar outcome was observed in a group of Mexican-Americans with mutated versions of CRTC3 that appeared to overstimulate the gene's effects. Researchers concluded that in the future, weight loss drugs may have to be customized to counter the effects of thrifty genes.
Epigenetics, a New Science
After the 13-year Human Genome Project was completed in 2003, scientists had identified the 20,000 to 25,000 genes present in DNA but realized that something besides an individual's genetic makeup also exerted a powerful influence. Somehow, biochemical signals activated or deactivated genes in response to environmental factors. This field of study became known as epigenetics, and its relationship to genetics is comparable to information technology: If the genome is the hardware, the epigenome is the software. Studies by Johns Hopkins University's Center for Epigenetics, published in the September 15, 2010, "Science Translational Medicine" isolated 13 genes with epigenetic "fingerprints" linked to obesity. Other studies, including one done at Baylor College of Medicine and published in the October 2008 "International Journal of Obesity" have suggested that "epimutations" in sperm and eggs caused by environmental stresses such as feast-famine cycles may be passed on to children and grandchildren, contributing to obesity and other serious health problems.
Balancing the Scales with Exercise
A Cambridge University study published in the August 2010 "Public Library of Science: Medicine" examined the effects of physical activity on more than 20,000 adults in the United Kingdom genetically predisposed to obesity. Researchers found that the benefits of daily physical exercise for this group outweighed those for a "genetically-protected" control group by about 40 percent. The study challenges the "deterministic view" that weight control efforts are pointless for people who consider themselves doomed by their DNA, wrote the author of an editorial, showing that "even the most predisposed people benefit from adopting a healthy lifestyle."
References
- Harvard Public Health Review, Fall 2010: Where DNA Meets Daily Life
- Johns Hopkins University: The JHU Gazette, Sept. 2010, Scientists Find Genes Related to Body Mass
- Minnesota State University: DNA and Chromosomes (Definitions)
- Baylor College of Medicine "From the Labs": Weight Increases Across Generations through Epigenetics, October 2008
- Public Library of Science: Medicine: Physical Activity Attenuates the Genetic Predisposition to Obesity, Aug. 2010
- Reuters: Too Fat? Study Fingers "Thrifty Gene" Suspect, Dec. 15, 2010
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