It is now well-established that overweight and obesity have a significant genetic component, with estimates of the contribution of genetic variation to observed variation in obesity-related phenotypes (such as BMI, fat mass, and leptin levels) ranging from 30 to 70 percent (Comuzzie et al., 1993, 1994, 1996).
The good news is that it is definitely possible to become big and muscular, even if you have a naturally slender frame. While genetics do play a role in determining our body types, they don't have to be a limiting factor in achieving your fitness goals.
From an analysis of around 100,000 children from six countries – including the United States – researchers found that around 20 percent of a child's body mass index (BMI) is inherited from their mother, while a further 20 percent is inherited from their father.
Researchers from the University of Essex found 14 “skinny genes” that may work together to assist with weight loss. Despite having these genes, scientists say that diet and other lifestyle factors are still vital for losing and maintaining a healthy weight.
Many studies have indicated a genetic component in determining obesity and body fat distribution [23,24,25]. Familial aggregation analysis, including twin and adoption studies, consistently estimate the heritability of BMI to be approximately 40–70% [26,27,28,29,30].
There are some genes associated with obesity and overweight. In some people, genes can affect how their bodies change food into energy and store fat. Genes can also affect people's lifestyle choices. There are also some rare genetic conditions that can cause obesity, such as Prader-Willi syndrome.
Lean muscle mass is more compact than fat. If you are muscular you can weigh quite a bit and not look fat. A person can be an ideal weight and have a lot of fat and look bulky. Another person can be overweight and have mostly muscle mass, and look lean and healthy.
Genetic and environmental factors interact to regulate body weight. Overall, the heritability of obesity is estimated at 40% to 70%. More than 244 genes have been found to strongly affect adiposity when overexpressed or deleted in mice.
This can be boiled down to good genes with a high metabolism, although experts say nutritional and behavioural factors could play a part to stave off the extra pounds of a person's body weight.
Some people have a naturally low BMI due to physical characteristics that run in their family. A high metabolism. If a person has a high metabolism, they may not gain much weight even when eating high-energy foods. Frequent physical activity.
Weight gain and short-term fluctuations may happen for a variety of reasons, such as aging or making lifestyle and dietary changes. However, fast weight gain can be a sign of an underlying health condition, such as a problem with the thyroid, kidneys, or heart.
Studies suggest that while your genes may determine up to 80 percent of your weight and body shape, environment and personal choice still play a significant role. So even if you're a dead ringer for your mother in old family photos, it doesn't mean you'll enter middle age with the same body.
So, as you start working out regularly and building strength, the new muscle you build may eventually weigh more than the fat you've burnt off. (Learn more about muscle weight vs. fat weight.) It often takes at least a month or two to add enough muscle to tip the scale, so don't be surprised if it happens.
You may be born naturally small and your low BMI can be due to your genes. You may have a very high metabolism and find it hard to put on weight, even if you eat foods that have a lot of calories. You may not follow a healthy, balanced diet because you forget to eat or cannot afford nutritious foods.
If genetic testing leads to the detection of genetic abnormalities that impact weight loss, a cure can then be found and a treatment plan can be made for lifestyle modification to help combat obesity. Hormone levels in the body affect weight loss.
Prader-Willi (PRAH-dur VIL-e) syndrome is a rare genetic condition that leads to physical, mental and behavioral problems. A key feature of Prader-Willi syndrome is a sense of being hungry all the time. People with Prader-Willi syndrome want to eat all the time because they never feel full. This is called hyperphagia.
For most individuals, though, height is controlled largely by a combination of genetic variants that each have more modest effects on height, plus a smaller contribution from environmental factors (such as nutrition).
While we have some control over our weight such as changing what we eat and how much we exercise, other factors are outside of our direct control such as genetics, environment and social determinants of health. Where we gain weight is even less so in our direct control.
So even though you may be losing fat, you're gaining muscle. You might feel slimmer, even as the number on the scale rises. “The scale doesn't tell the entire story,” said exercise physiologist Christopher Mohr, PhD, RD. “Since muscle and fat take up different volume, they look very different on the body.”
According to Dr. Cerna, for some people, BMI can be skewed. “If you have a lot of muscle mass, such as in athletes and bodybuilders, your BMI will be overestimated. In seniors and people with less muscle mass, BMI may be underestimated,” said Dr.