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Genetics + Weight Loss: Can DNA Tests Help Clients Get Fit?

DNA tests are all the rage these days. For a very reasonable price, anyone can get their DNA sequenced. Some do it to learn their family history and ethnic ancestry, while others want to know if they are prone to serious illnesses. 

What these tests can do for you as a trainer is to help you give your clients a DNA-based program for weight loss or maintaining a healthy weight. It can be frustrating for you, but mostly for your clients, when they try but don’t lose weight. What’s happening? Is it genetic?

Genes aren’t everything, but the more we know about our DNA the more we understand how genetics impact weight. Some people gain weight easily and are overweight for most of their lives, while others are naturally thin. Learn more about this connection and how it can help you better help your clients. 

Genetics and Weight Loss – Is There Really a Connection?

Even without the scientific research, it’s not hard to see that our genes play a role in weight. Some people simply struggle more than others to maintain a healthy weight, and you often see this run in families. 

There is also plenty of official evidence from studies that our genes do in fact impact our weight. 

Yes, there is a connection between genetics and weight. It is important that your clients understand this but also that their lifestyle choices and environments contribute to weight gain and obesity. Gaining and losing weight is complex. A person’s DNA only dictates about 40% of what actually happens, that other 60% is their lifestyle and environment.

How Does DNA Impact Weight Loss?

When it comes to a person’s ability to lose weight, there is not one single gene that will dictate that. However, there is a combination of genes that will dictate how quickly or slowly they will lose weight. When looking at a person's ability to lose weight, the main traits considered are their weight loss ability with diet and exercise, fat loss response to cardio, and body composition response to strength training. 

These traits combined will give the trainer the best insight as to how easily their client will be able to lose weight. 

Weight Loss Ability with Diet and Exercise

This is a unique trait that can tell the personal trainer just how hard the client will need to work to get the results they are looking for. For the trainer, it allows them to give the client realistic goals and timelines in which they can expect to achieve those weight loss goals.

For example, suppose a trainer has two clients who train together. One has a genotype that shows it will take a little longer to lose weight but the other has a genotype that allows them to lose weight pretty easily. The trainer can then have separate conversations and explain to them why they should not compare results with each other and what they specifically need to do to reach their own unique goals.

Fat Loss Response to Cardio

The fat loss response to cardio trait is one of those traits that can help clients stick to an exercise plan. This trait tells the trainer how their client’s body uses fat stores in cardio exercise. When you think about personal training clients, most give up when they are not hitting their goals. This trait will tell the trainer from the start how long do they need to perform cardio exercise to lose fat. Not only how long, but it will also tell them how many days a week is ideal and at what intensity. It truly unlocks secrets that could take a trainer and client years of working together to figure out. 

Body Composition Response to Strength Training 

Trainers hear from their clients how they want to get more toned and lose weight but they’re not sure how to achieve that. This is where this genetic trait comes in handy. Body composition response to strength training will tell the trainer how often this client needs to strength train to improve their body composition. This can include fat loss, increase in strength, or increase in muscular size. Not only will this tell the trainer how often they should strength train but based on their DNA even what type of strength training they should perform all the way down to what sort of weights they should be using. 

How Genes Effect Weight – From Cravings to Coping with Stress

Clearly, the genetic component of weight gain and weight loss is complicated. There are many ways in which genes can influence your weight. Here are some other ways genes impact weight and weight loss: 

  • How much food it takes to feel full
  • Metabolic rate
  • Body composition
  • Cravings and appetite
  • Using food as a way to cope with stress
  • How the body responds to cardio or strength training
  • How the body responds to macronutrient ratios in the diet

Working with Clients on a Personalized Weight-Loss Plan

While the new science of using DNA to inform weight loss is far from perfect, it does have huge potential and is moving forward at a rapid pace. You can help your clients by encouraging them to get DNA tests specific to nutrition and weight and then help them use that information to make personalized plans. 

Examples from Research

A good example of how personalized, genetic-based programs can be useful comes from two studies. One, conducted in 2012, found that people experience higher fat loss when on a high-protein diet. The participants all had a specific gene variant (1).

A study from 2018 seemed to contradict the idea of personalization by showing that there were no differences in weight loss between people on a low-fat diet and those on a low-carb diet. These participants simply may not have had the right gene variants for the diet they were put on (2).

What’s Included in a DNA Report?

If you can help your clients determine their own personal genetic variants that impact weight, they can take steps to diet and exercise more effectively. There are several pieces of information a genetic test focused on weight, exercise and diet will provide that you can use in making a plan for a client: 

  • Specific genetic traits related to weight loss
  • Overall ability to lose weight
  • The body’s ability to utilize each macronutrient
  • Nutrient levels
  • The ability to lose fat from doing cardio or strength training
  • The ability to change body composition from strength training
  • The ability to get fit with cardio exercise
  • Health and weight indicator responses to cardio, such as insulin sensitivity and blood glucose 

Using the DNA Report

A comprehensive genetic test report will come with built-in recommendations for the individual. But this is where you can use your expertise as a trainer and your knowledge of your client to truly personalize the plan. 

For instance, if the report recommends a client do cardio just three days a week, but you know this person enjoys running, don’t deter them. The report may indicate they need to add in more strength training than you’re currently doing, but that doesn’t mean you need to cut back on the exercise they enjoy. 

It will also help if you do your research to understand what specific genes do and how they impact weight. For instance, people who have certain variations in the FTO gene tend to eat more, crave foods more, and get full less easily. So, they generally weigh more. 

One way to combat this genetic issue is to encourage a client to be more active generally. Getting up from the desk at work for quick exercises, a walk at lunch, doing hobbies that are active like gardening, plus regular training sessions can help these clients maintain a healthier weight. In other words, they simply need to move more than other people. 

As you work with a client on developing a personalized, DNA-based plan you may come across some issues beyond your scope. Always be prepared to advise a client to see their doctor about things like persistently failing to lose weight, high blood sugar, and any troubling symptoms associated with working out or dieting. 

A personalized weight-loss and exercise plan based on genetics can be a powerful tool. But, it can also backfire, as with any tool. As a trainer it’s your job to educate your clients about what the genetic test results mean for dieting and weight loss. Help them understand this is just one piece of the puzzle and they still have the power to make positive changes with their choices and actions. 

Support your clients’ fitness and weight loss journeys by completing the ISSA’s course for DNA-Based Fitness Coaching. You'll help your clients with more precise answers to the whys of their fitness questions and be more equipped to build the programming specifically tailored for them.



  1. Zhang, X., Qi, Q., Zhang, C., Smith, S.R., Hu, F.B., Sacks, F.M., Bray, G.A., and Qi, L. (2012, November). FTO Genotype and 2-Year Change in Body Composition and Fat Distribution in Response to Weight-Loss Diets: The POUNDS LOST Trial. Diabetes. 61(11), 3005-11. doi: 10.2337/db11-1799. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22891219
  2. Gardner, C.D., Trepanowski, J.F., Del Gobbo, L.C., Hauser, M.E., Rigdon, J., Ioannidis, J.P.A., Desai, M., and King, A.C. (2018, February). Effect of Low-Fat vs Low-Carbohydrate Diet on 12-Month Weight Loss in Overweight Adults and the Association With Genotype Pattern or Insulin Secretion: The DIETFITS Randomized Clinical Trial. JAMA. 319(7), 667-79. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/29466592

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