Submitted by Amy Sercel MS RD CD
Edited by Marcia Bristow MS RDN CSSD CD
It seems like it couldn’t get any better: a
nutrition plan truly tailored just for you, created using your genetic
blueprint. Is this the answer to fad
dieting, weight cycling and frustration?
Unfortunately, it appears that the science just isn’t quite there yet,
and the promises from “DNA diet” companies might be too good to be true.
The premise behind the DNA diet makes
sense. Your genes hold information about
your chance of getting certain diseases, such as obesity, diabetes, or high
cholesterol.1 You can influence whether or not your body expresses certain
genes by becoming more physically active or making different food choices. There are even genetic markers that suggest
whether you may be better able to metabolize fat or carbohydrates,2 which in theory would determine whether you should eat a high-fat
or high-carbohydrate diet.
A recent study called DIETFITS examined this
theory by placing 600 participants on either a high-fat or high-carbohydrate
diet. The participants got regular
instruction about weight loss strategies while following their assigned
diet. During the course of the study,
the researchers categorized participants as “low-fat genotype,”
“low-carbohydrate genotype,” or “sensitive to neither genotype” depending on
whether their DNA contained any of three different variations. After one year,
participants on the high-fat diet had lost about the same amount of weight as
the people on the high-carbohydrate diet, regardless of their genotype, and
whether they followed the diet that “matched” their genetic sensitivity to fat
or carbohydrates.2
The DIETFITS study also gave participants a
glucose tolerance test to see whether their insulin sensitivity was related to
their success with weight loss on a low-carbohydrate vs. low-fat diet. Researchers believed that people who were
insulin resistant would do better on a low-carbohydrate diet. After one year, however, researchers found
that glucose tolerance had no impact on weight loss for people in either the
low-carbohydrate or low-fat group.2
Part of the reason it’s so difficult to
accurately match a person’s genes to their ideal diet is that many different genes
are associated with weight, and your environment and behaviors influence how
these genes will be expressed.1 For example, a high activity level is associated with a stronger
immune system, possibly because being active triggers small amounts of
inflammation, and as a result the body makes more copies of the proteins needed
to fight inflammation.3 In order to say for sure whether DNA diets are truly the thing of
the future, there will have to be more, well-designed research studies that
evaluate the expression of more than just three genes, and follow participants
for longer than just one year. This way,
researchers will be able to say whether the diets support both weight loss and
weight maintenance over time.
In the meantime, if you’re still curious
about the DNA diet, there are many companies that can perform this service for
you. The cost ranges from about $50 to
$200, depending on the depth of information and amount of support you
receive. Most of the tests ask you to
send in a saliva sample so they can map your DNA. Some also measure your insulin sensitivity
and other markers of disease risk like cholesterol and triglycerides to help
you create a meal plan that will maximize your overall health in addition to
promoting weight loss. For example, if a
test measures your insulin sensitivity, they send a glucose tolerance test, in
which you would drink a high-carbohydrate beverage, wait about 30 minutes,
prick your finger and collect a blood sample to send back and be analyzed. If your cells are sensitive to insulin, you
will have less glucose remaining your blood.
If you are insulin resistant, your blood sugar may be higher. Insulin resistance is a precursor to
diabetes, so if you have a family history or other risk factors for this
disease, you’ve probably had a glucose tolerance test at a doctor’s visit.
These companies’ websites do not include many
specific details of how the test results inform their recommendations (they’re
probably trade secrets!). Most likely,
if someone’s test indicates they’re insulin resistant, they will be given a
low-carbohydrate meal plan to help reduce their chances of getting
diabetes. Along the same lines, if
someone’s blood test suggests they have high triglycerides, that person will
likely be given a low-fat meal plan.
These findings would be used in combination with the results of the
saliva sample DNA test. Marcia is
ordering a test kit to learn more about the process and will be able to provide
more information about this in the near future.
It’s important to note that even without a
personalized DNA diet plan, you can still make healthy diet and lifestyle
choices that will impact your overall health and reduce your risk of
disease. In one study, men with low-risk
prostate cancer adopted a low-fat diet, increased their activity level to be
active for about 4 hours per week, and spent time prioritizing stress
reduction. After 3 months, genetic
evaluation showed that they were producing fewer of the genes associated with
tumor development.1 In the DIETFITS study, all of the participants were told to eat
more vegetables, eat less added sugar and refined grains, and focus on whole,
unprocessed foods whenever possible.2 You will likely see similar health benefits and reduce your risk
of disease by practicing stress reduction, getting active, eating more fruits
and vegetables, and eating fewer refined grains. For support with this, contact a Registered
Dietitian who will give you evidence-based recommendations that work with your
lifestyle to reduce your risk of disease over the long-term and reach any other
nutrition-related goals you might have.
References:
1. Camp KM, Trujillo E. Position of the
Academy of Nutrition and Dietetics: Nutritional Genomics. J Acad Nutr Diet.
2014;114(2):299-312. doi:10.1016/j.jand.2013.12.001
2. Gardner CD,
Trepanowski JF, Gobbo LCD, et al. 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.
2018;319(7):667-679. doi:10.1001/jama.2018.0245
3. Gjevestad GO,
Holven KB, Ulven SM. Effects of Exercise on Gene Expression of Inflammatory Markers
in Human Peripheral Blood Cells: A Systematic Review. Curr Cardiovasc Risk
Rep. 2015;9(7). doi:10.1007/s12170-015-0463-4
