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Obesity…Is It Hidden In Your Genes?

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Genetics, or the inherited code that controls the metabolic processes in the human body, plays a part in all aspects of weight gain, weight loss and weight maintenance. There are some individuals that never need to diet and seem to be able to eat all types of foods without any weight gain. There are also other individuals that struggle all their lives with weight management even though they may eat healthier than others people and exercise on a regular basis. Understanding the role that genetics plays in weight loss, weight gain and weight management can help in choosing the best type of diet, exercise routine and lifestyle to effectively reach weight loss goals.

In studies with twins, it was determined that weight gain became more pronounced in twins that were less active. These same inactive twins had higher bad cholesterol levels and higher body mass indexes (BMI) than their brothers or sisters that were moderately active. This study used twins where one was a vigorous and routine exerciser compared to a twin that was sedentary. 1 This research replicated an earlier twin study in 1994 that was exclusively done with male twins. Results of that study indicated that approximately 50% of weight gain was genetically controlled and lifestyle choices and environmental factors, including exercise, contributed to the chance of weight gain and obesity.

Metabolic Rate And Weight Gain

Metabolic rate is a key factor in weight gain, weight loss and weight maintenance since it is largely controlled by genetic factors. The metabolic rate determines how much energy is burned at the resting state and how long elevated rates occur after exercise. Individuals and families with higher resting metabolic rates have lower incidence of weight gain and obesity without any specific dieting or exercise regimes in place. Conversely those people and families with lower resting metabolic rates have higher incidents of weight gain and obesity.

As part of the metabolic process, glucose metabolism is also affected by genetic factors. Higher metabolism of glucose in the blood results in increased weight gain while lower levels of glucose metabolism is less likely to cause weight gain when the same diet is consumed. This factor has been studied in pregnant women that are at risk for gestational diabetes and excessive weight gain during pregnancy. In one study in Finland it was found that, even with intensive dietary counseling after which women choose whole grain breads and increased the servings of fresh fruits and vegetables consumed per day, excessive weight gain was not prevented.However, the study did show that women that received the specific dietary counseling and ate healthier foods had normal birth weight babies while the control group that received only standard maternity counseling gave birth to 15% of babies that were considered high birth weight.

 Types of Diets and Genetics

 There has been interest in the relationship of genetics and the effectiveness of one type of diet over the other. In studies of large numbers of obese individuals, different diets were used that were hypo-energetic low fat or high fat diets. Each individual was placed in one of two groups, both consuming diets that were fewer than 600 kcal/day, with one group allowed 20-25% of the caloric intake in fat and the other group allowed 40-45% of the energy intake in fat.

The groups were further divided into those that had genetic markers for appetite regulation and fat tissue development and fat tissue functioning. The results of the long term trial, which included 771 participants of all ages, showed that the genetics had little impact on the weight loss exhibited by those on the low or high fat diet options. 3

Finding The Fat Gene

 Although researchers continue to strive to locate the specific gene that controls weight gain and fatty adipose tissue development in the body, there is still no specific identification. Researchers believe that it may be a combination of genes, including appetite regulation, fatty tissue function and metabolic regulation that ultimately control the amount of fatty tissue that is deposited in the body.

Genetic research has led to a greater understanding that different genetic combinations are more appropriate for achieving weight loss on low carbohydrate and low fat diets. They have identified three factors that are responsible for fat restriction in the body – hepatic phosphofructokinase, histamine N-methyl transferase, and retinoic acid receptor beta. The angiotensin receptor Type II is partially responsible for restricting carbohydrate use in the body. Genetic testing in the future for the associated genes for carbohydrate and fat restriction may help in determining a targeted diet that will be most effective for any given individual. 4

 The Future Of Genetics In Weight Loss

 Genetics does play a component in weight loss, weight gain, weight maintenance and obesity. The science to determine specifically what genetic combination increases the likelihood of obesity or overweight is not yet understood. It is important to keep in mind that genetics is not the major factor in weight loss or weight gain, it is only a component. Increasing physical activity while decreasing caloric intake will reduce weight in all individuals. Finding a diet that assists with maximum weight loss while maintaining healthy food choices and nutrition should be done on an individual basis depending on how your body responds to the levels of fats and carbohydrates in the respective diet.

References

1 Williams, P. T., Blanche, P. J., & Krauss, R. M. (2005). Behavioral Versus Genetic Correlates of Lipoproteins and Adiposity in Identical Twins Discordant for Exercise. Circulation , 350-356.

2 Kinnunen, T. I., Pasanen, M., Aittasalo, M., et al. (2007). Preventing excessive weight gain during pregnancy – a controlled trial in primary health care. European Journal Of Clinical Nutrition , 884-891.

3 Sorensen, T. I., Boutine, P., Taylor, M. A., et al. (2006). Genetic Polymorphisms and Weight Loss in Obesity: A Randomised Trial of Hypo-Energetic High- versus Low-Fat Diets. PLoS Clinical Trials .

4 Seip, R. L., Volek, J., Windemuth, A., et al. (2008). Physiogenomic comparison of human fat loss in response to diets restrictive of carbohydrate or fat. Nutrition and Metabolism .

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