Conventional nutritional and fitness wisdom teaches us that in order to lose weight, you have to burn more calories than you take in. One pound is equivalent to about 3,500 calories. So let’s say, assuming your weight is currently stable, that you adjust your diet so that you consume 500 fewer calories per day, or you increase your activity level so that you burn 500 more calories, or some combination of the two. After a week, you should lose one pound.

However, as many people can attest to, it doesn’t always work that way. This approach to weight loss is a bit over-simplified. The way our bodies store and utilize energy is subject to a number of complex metabolic processes. This is a good article that looks at a lot of different factors related to energy metabolism, but today I want to look at it from a different angle: genetics.

Everyone reacts to food differently

A wave of research in recent years — made possible by the Human Genome Project — has identified literally hundreds of genetic variants that affect our health. These genetic variants influence how we process different foods, how we react to certain exercises, and how our bodies store and burn energy (i.e. fat).

I’ve mentioned in a few different places throughout this website that I never really considered going ketogenic until a DNA fitness test revealed that I was genetically predisposed to benefit from a low-carb diet. What else did this test tell me? I have the “sprinter gene,” which makes me capable of explosive bursts of energy (who knew??). I’m a fast caffeine metabolizer, which means I am more likely to benefit from healthful compounds in coffee (yay!). I’m a “bitter taster,” which explains why I tend to use a lot of salt on my food. I also produce lower levels of adiponectin, a hormone that regulates a number of processes related to insulin sensitivity and glucose metabolism. This partially explains why my ideal matching diet type is low-carb: As a carrier of the ADIPOQ variant, I am less effective at using glucose for energy, which would normally put me at a higher risk of type 2 diabetes.

How your genetics affect your weight

The ADIPOQ variant is pretty common: Up to 85 percent of the population carries some version of it. And that’s just one example of how a genetic variant can affect your weight. Let’s look at a few others:

  • Genes known as the PPAR genes control processes related to energy metabolism and storage. The PPAR genes are also involved in the growth of fat tissue and the synthesis of fat cells. A variant in one of them, the PPARG gene, can make carriers more sensitive to dietary fat, increasing the risk of obesity and type 2 diabetes. Another variant has the opposite effect, leading to an impaired ability to convert food into fat.
  • A variation in the FTO gene causes higher levels of ghrelin, the hormone that signals hunger. Carriers of this variant typically feel hungry again soon after eating, tend to choose higher-calorie foods, and are 70 percent more likely to become obese.
  • A variant in the NMB gene is associated with increased hunger and an increased risk of obesity.
  • The TAS2R38 gene — the same one that makes people sensitive to bitter flavors — is also associated with increased eating disinhibition, or the tendency to eat more than normal in certain situations.

With so many factors at work, it’s no wonder that weight loss can be incredibly frustrating … that fad diets only work for a few people … that two people can eat the exact same diet and experience drastically different results.

So what does this mean for you? First of all, if you’ve struggled to lose weight, or tend to regain weight after you’ve lost it, stop beating yourself up over it. It isn’t necessarily a matter of willpower.

It also means that there is no one ideal diet that works for everyone. I’ve experienced great results on keto, but it isn’t for everyone. For some people, a high-fat diet can lead to problems, and may not be the answer for weight loss.

As a side note, I recommend focusing not on the quantity of your calories but on the quality and the source. A cup of blueberries and a snack pack of Pringles are both about 100 calories. I don’t have to tell you which one is better for you. Here’s a post I wrote about the calorie deception on my holistic health blog.

If you’re curious about how your own genotype affects your weight and your health, you can order a direct-to-consumer genetic test. The test I took was through Vivaliti DNA. They provide a 49-page report with information on how more than 80 different genetic markers affect your health. You can also add on a personalized genetic blueprint that provides actionable steps for helping you make sense of it all, or you can sign up to work with a health coach if you need a little extra support to meet your health goals.

Full disclosure: Vivaliti DNA is a client of mine, but I do not benefit financially from sales of their genetic test.