Can DNA Testing Be Used for Dieting? Explaining the Difference from DNA Profiling

Rewritten on: July 3, 2024

This article explains the difference between DNA profiling and DNA genetic testing, and details why using DNA testing for dieting purposes cannot currently be recommended due to a lack of scientific evidence. It also covers how to identify reputable providers, the balance between genetic and environmental factors, and the future potential of precision nutrition.

Understanding the Difference Between DNA Profiling and DNA (Genetic) Testing

Many people may have come across information claiming that "DNA testing can reveal the best method for dieting." Through television programs, social media, and internet advertising, we increasingly see claims such as "checking your own DNA reveals whether you have a tendency to gain weight" or "genetic testing can find the diet method suited to you." However, to correctly understand this topic, it is first necessary to clearly grasp the difference between two concepts: "DNA profiling" and "DNA (genetic) testing." Because these terms sound similar, they are often confused, but they differ greatly in both purpose and method.

DNA profiling is a non-clinical molecular biology testing method used to identify individuals and determine blood relationships. Specifically, it analyzes the patterns of short repeating sequences (STR: Short Tandem Repeat) present in the human genome, allowing individuals to be identified with extremely high precision. STRs are scattered throughout human DNA, and because the number of repetitions differs from person to person, they function as a kind of "biological fingerprint" for personal identification [ref:1]. Because of its high reliability, this technique is used in a wide range of applications, from criminal investigations by police and legal evidence presented in court, to personal testing aimed at confirming parent-child relationships. As DNA profiling technology continues to evolve daily, it is expected to be applied across an even wider range of fields, particularly in law enforcement and the judicial system.

On the other hand, DNA (genetic) testing refers to DNA analysis methods used for clinical or health-promotion purposes, such as disease treatment and prevention, new drug development, and analysis of an individual's physical constitution. This method reads genetic variations called SNPs (single nucleotide polymorphisms) to examine how specific genes are related to an individual's constitution or disease risk [ref:1]. For example, by examining whether a particular SNP is associated with risk of diabetes or heart disease, clues for preventive medical intervention can be obtained. Recently, there has been a trend toward applying this genetic analysis technology to optimizing diet and exercise programs.

Because each person's DNA is different, the perception is spreading that analyzing one's constitution from DNA could make it possible to develop individually tailored, efficient training methods and dietary approaches. Many people would surely want to try this if it could help solve obesity problems, contribute to medicine, or improve the performance of athletes.

What is important here, however, is that "DNA profiling" and "constitutional analysis through genetic testing" are entirely different things. DNA profiling is a technology specialized for personal identification and proof of blood relationships, not for analyzing constitution or suitability for dieting. If you use a service advertised as "diet through DNA testing" without understanding this fundamental difference, you risk not only failing to get the results you expect, but also being swayed by information that lacks scientific grounding.

It should also be added that the STR regions used in DNA profiling are located in non-coding regions of the genome (portions that do not code for proteins) and do not directly affect gene expression or physical constitution [ref:3]. In other words, it is fundamentally impossible to derive constitutional information such as "this person tends to gain weight from carbohydrates" or "this person's body tends to store fat" from STR analysis results. Correctly understanding this point is a basic yet extremely important form of literacy for avoiding being misled by inaccurate information.

Why Is Confusion So Common? The Similarity of Terms and Its Impact on Consumers

The biggest reason "DNA profiling" and "DNA genetic testing" are so easily confused is that both include the common keywords "DNA" and "testing." For the general consumer, it is difficult to recognize that these are entirely different technologies, and they tend to lump both together as simply "DNA testing." Because some providers exploit this gap in understanding to sell diet-related services with weak scientific grounding, considerable caution is needed.

In fact, Japan's Consumer Affairs Agency and the National Consumer Affairs Center have received consultations regarding genetic testing kits, with reports such as "the results were vague and unhelpful" and "I couldn't understand the scientific basis" [ref:5]. To avoid such trouble, thoroughly understanding the essential difference between "DNA profiling" and "DNA genetic testing" is the first step in protecting yourself as a consumer.

In addition, various names such as "genetic diet," "DNA diet," and "gene diet" are used in the media and online, and this lack of consistency in terminology adds to consumer confusion. In scientific contexts, precise terms such as "nutrigenomics" and "precision nutrition" are used, but vague names tend to be preferred as marketing catchphrases. This kind of information asymmetry is one factor making it difficult for consumers to make appropriate judgments.

Why Using DNA Profiling for Dieting Cannot Be Recommended

To state the conclusion up front: at this stage, using DNA profiling for dieting cannot be recommended. This may be disappointing news for those who have repeatedly tried and failed at dieting, or who struggle to see results despite their efforts. However, as a matter of scientific fact, multiple studies have shown that environmental factors such as daily eating habits, exercise levels, sleep quality, and stress management have a far greater influence on diet success than innate genetics.

Of course, it cannot be denied that genes play some role in an individual's basal metabolic rate, tendency to build muscle, and tendency to accumulate fat. For example, genes such as FTO and MC4R are known to be associated with obesity risk, and there are reports that people with these gene variants tend to gain weight more easily [ref:2]. However, the influence of each individual gene is extremely small, and a meaningful conclusion cannot be drawn without comprehensively evaluating the hundreds of related genes as a whole. As genetic research advances further in the future, entirely new approaches to dieting or groundbreaking training programs based on an individual's DNA information may well be developed. However, the scientific reality is that we have not yet reached that stage.

Specific Reasons Why Diet DNA Testing Is Not Reliable

So why can't the "diet DNA testing" currently offered be trusted scientifically? The main reasons are summarized below.

• Hundreds of genes are said to be related to obesity, so determining a diet strategy based on just a few specific genes is scientifically insufficient [ref:2]
• Large-scale, reproducible clinical research confirming the relationship between genes and weight change has not yet been sufficiently accumulated
• There is no reliable evidence that diet plans derived from genetic information are significantly superior to conventional calorie restriction and exercise guidance [ref:4]
• Among providers of DNA paternity testing worldwide, only a very small number also offer diet DNA profiling, and this is far from an industry standard
• Numerous epidemiological studies show that the influence of environmental factors (eating habits, exercise levels, gut microbiota, hormone balance, etc.) generally far outweighs genetic factors
• Commercial diet genetic testing kits analyze only a limited number of SNPs, covering just a tiny fraction of the entire genome
• Many cases have been reported in which people with the same genotype have significantly different body shapes and weights due to differences in living environment and food culture

There are currently several universities and research institutions in Japan and abroad conducting genetic research, but unfortunately, no credible peer-reviewed papers or research results have yet emerged showing that DNA profiling can be used at a practical level for dieting or sports training. In a large-scale clinical trial (the DIETFITS study) published by Stanford University in 2018, no significant difference in weight loss was found between a diet assigned based on genotype and a diet assigned randomly [ref:4]. Therefore, the conclusion remains unchanged: at this stage, the most effective diet method is still to steadily continue balanced dietary management and moderate exercise.

Correctly Understanding the Balance Between Genetic and Environmental Factors

To correctly understand the relationship between genetic and environmental factors in dieting, it is important to recognize that "genes indicate a tendency in constitution, not a predetermined destiny." Epidemiological data from twin studies estimate the heritability of obesity at roughly 40–70%, but this does not mean that "genes alone determine whether you gain weight." Heritability is a statistical measure that indicates the proportion of variance explained at the population level; it does not mean that, at the individual level, "70% of your obesity is due to genetics" [ref:2].

In fact, obesity rates have surged worldwide over the past few decades, yet the human genome has not changed significantly in such a short period. It is scientifically reasonable to attribute this rise in obesity rates to environmental factors such as changes in the food environment (the spread of high-calorie foods and increase in processed foods), decreased physical activity (more desk work, greater reliance on cars), reduced sleep time, and increased stress. In other words, while genes are not entirely irrelevant, there is no doubt that improving daily lifestyle habits is the key to successful dieting.

According to a report by the World Health Organization (WHO), the global obese population has more than tripled since 1975. This rapid change cannot be explained by changes to the human genome, which does not shift significantly over just a few generations, strongly suggesting that dramatic changes in the food environment and lifestyle are the main cause. Therefore, rather than placing excessive hope in the results of genetic testing, reviewing one's own living environment first is the most scientifically sound approach.

Checkpoints for Identifying Providers That Offer Diet DNA Testing

If you search online using keywords such as "DNA diet" or "genetic testing for weight loss," various services will appear. Some providers claim that "DNA can reveal anything," while others claim to use technology "developed by a famous university" to even assess human talents and abilities. However, considerable caution is needed with such information. There have been many cases in which people paid high fees for services that are not yet scientifically established, only to end up with no useful information [ref:5].

Steps for Judging Whether a Provider Is Trustworthy

If you find a service offering "diet DNA testing," try checking its trustworthiness using the following steps.

1. Check whether the service's official website references or links to peer-reviewed academic papers or specific research results that form its theoretical basis
2. Check whether the provider has ISO certification or accreditation from a government agency or other trustworthy third-party body in any country
3. Search academic databases such as PubMed or Google Scholar to confirm whether the papers cited actually exist
4. Investigate whether experts such as physicians or genetic counselors are involved in interpreting the results
5. Watch for exaggerated advertising or the overuse of absolute terms such as "100%" or "guaranteed"
6. Check user reviews and feedback from multiple sources to see whether the feedback reflects genuine scientific findings
7. Confirm that a clear privacy policy is provided regarding the handling of personal genetic information

Many providers of questionable reliability do not specify concrete paper titles or research institution names, instead using vague language to create the impression of scientific backing. Even if a provider uses phrases like "based on the latest genetic science" or "proven with data from tens of thousands of people," be cautious if the source of that evidence is not clearly stated. Such providers may simply lack sufficient knowledge of genetics, or may be attempting to mislead consumers for commercial purposes.

Also pay attention to the content of the reports provided as genetic test results. If a report draws a definitive conclusion — such as "you are a type that gains weight easily from carbohydrates" or "you have a constitution that should avoid fat" — based on just a single SNP, its reliability must be considered extremely low. An extremely large number of genes are associated with obesity and dieting, and they interact in complex ways, so it is currently impossible, given the state of science, to determine an individual's diet strategy based on just a few SNPs [ref:2].

Future Possibilities and the Approach to Take Now

Genetic analysis technology is advancing year by year, and the day may come when personalized nutrition (precision nutrition) based on an individual's genomic information becomes practical. In fact, the research field of nutrigenomics — the study of nutrition genetics — is developing rapidly, and knowledge about the interaction between genes and diet is steadily accumulating [ref:2]. With the spread of next-generation sequencers, analysis costs have dropped dramatically, and larger-scale genome-wide association studies (GWAS) are being conducted around the world. This is expected to identify more obesity-related genes in the future, potentially enabling detailed nutritional guidance tailored to an individual's genetic background.

However, before this can be established as a reliable service for consumers, many more large-scale clinical trials and reproducibility verifications will be needed. It typically takes more than ten years for laboratory-level discoveries to reach actual clinical application, and it is difficult to say that the diet genetic testing kits currently on the market have sufficient academic reliability at this time.

At present, those who wish to succeed at dieting are best served by consulting experts such as registered dietitians or physicians, rather than relying on genetic testing, and working to establish reasonable dietary improvements and exercise habits suited to their own lifestyle. This is the most reliable and scientifically supported method available.

Epigenetics and Dieting — Understanding the Gene "Switch"

One concept often overlooked when considering the impact of genes on dieting is epigenetics. Epigenetics refers to a phenomenon in which patterns of gene expression change even though the DNA sequence itself does not change. Put simply, genes have "on" and "off" switches, and the flipping of these switches is greatly influenced by living environment, diet, exercise habits, stress levels, and even nutritional status during fetal development.

For example, epigenetic changes such as DNA methylation and histone modification are known to regulate the expression of genes involved in fat cell differentiation and lipid metabolism. This is considered one reason why even identical twins with the same gene sequence can end up with different body shapes and weights due to differences in their living environment and eating habits after growing up. In other words, even if the genetic "blueprint" is the same, which parts of that blueprint are actually read out is greatly influenced by acquired environmental factors.

This knowledge of epigenetics carries extremely important implications for dieting. This is because, even if someone carries a gene variant associated with obesity risk, it may be possible to suppress the expression of that gene through appropriate diet and exercise. Conversely, even someone considered to have genetically low obesity risk can still become obese if they continue unhealthy lifestyle habits. This further shows that the simplified view that "body shape is determined by genes alone" is not scientifically accurate, and highlights just how important lifestyle improvement really is.

The Relationship Between Gut Microbiota and Obesity

In recent years, the role of the gut microbiota has rapidly attracted attention in the context of dieting and weight management. Tens of trillions of bacteria live in the human gut, and this community of bacteria has been shown to be deeply involved in food digestion and absorption, regulation of immune function, and even energy metabolism.

Interestingly, multiple studies have reported that the composition of gut microbiota differs between obese individuals and those of healthy weight. Specifically, it has been suggested that the ratio of Firmicutes to Bacteroidetes may be related to obesity, and the hypothesis that improving the gut environment could have a positive effect on weight management is being investigated.

This gut microbiota is a factor independent of the host's DNA sequence. In other words, even if DNA testing analyzes an individual's genome, it cannot reveal the state of the gut microbiota. Given that the gut environment may contribute significantly to diet success, the limitations of building a diet strategy based solely on DNA testing results become even clearer. Improving the gut environment through a fiber-rich diet, consumption of fermented foods, and use of probiotics are healthy approaches recommended for everyone, regardless of genetic test results.

Concrete, Scientifically Established Steps for Diet Success

To succeed at dieting based on scientific evidence rather than relying on genetic test results, the following concrete measures are recommended. All of these are methods whose effectiveness has been confirmed through large-scale epidemiological studies and meta-analyses.

• Track your total daily calorie intake and stay mindful of the balance with calories burned — using a food-logging app can make this more effective
• Aim for a balanced diet of protein, fat, and carbohydrates, with particular attention to sufficient protein intake, which helps maintain muscle mass and prolongs satiety
• Make a habit of at least 150 minutes per week of moderate-intensity aerobic exercise (walking, jogging, swimming, etc.), combined with resistance training at least twice a week
• Ensure 7–8 hours of adequate sleep to prevent the rise in ghrelin (an appetite-stimulating hormone) and the drop in leptin (a satiety hormone) caused by sleep deprivation
• Avoid accumulating stress by setting aside time for mindfulness and hobbies, which helps suppress fat storage caused by cortisol (a stress hormone)
• Avoid extreme dietary restriction and choose sustainable methods you can maintain over the long term — excessive restriction is the leading cause of rebound weight gain
• Actively consume vegetables, fruit, and whole grains rich in dietary fiber to improve gut health and stabilize blood sugar levels
• Drink enough water — dehydration can lower your metabolic rate and cause you to confuse thirst with hunger

These lifestyle improvements have been scientifically proven to be effective regardless of a person's genetic background. Before spending large amounts of money on genetic testing, practicing basic health management methods like those above is the most cost-effective diet strategy.

DNA testing technology is an extremely reliable tool for its original purposes, such as paternity testing and criminal investigation. seeDNA Genetic Medical Research Institute provides scientifically grounded DNA profiling services under a system that has obtained the international quality standard ISO 9001 and Japan's Privacy Mark for personal information protection. However, regarding its application to dieting, we recommend watching carefully until sufficient scientific evidence has accumulated. While genetic research is advancing remarkably, and a truly personalized diet program utilizing an individual's genomic information may eventually become a reality, it is wiser at this stage to focus on scientifically established health management methods you can put into practice right now, rather than waiting for that day to come.

Frequently Asked Questions

Q1. What is the difference between DNA profiling and DNA genetic testing?

A. DNA profiling is a non-clinical testing method that analyzes STRs (short tandem repeats) to identify individuals and prove blood relationships, and it is used in criminal investigations and paternity testing. DNA genetic testing, on the other hand, is clinical/health-oriented analysis that examines SNPs (single nucleotide polymorphisms) to analyze constitution and disease risk. Although the names are similar, the purposes and methods are entirely different.

Q2. Is it true that DNA testing can reveal the best method for dieting?

A. At this stage, there is not sufficiently reliable scientific evidence that a diet method can be determined based on DNA test results. Even in Stanford University's large-scale clinical trial (the DIETFITS study), no significant difference in weight loss was found between a diet based on genotype and a conventional diet [ref:4]. Because environmental factors such as eating habits and exercise levels have a far greater influence on diet success than genetic factors, its use cannot currently be recommended.

Q3. How can I judge the trustworthiness of a provider offering diet DNA testing?

A. Check whether the service clearly cites peer-reviewed academic papers as its theoretical basis, whether it holds accreditation such as ISO certification from a trustworthy body, and whether experts such as physicians or genetic counselors are involved in interpreting the results. Also confirm that any cited papers actually exist on PubMed or Google Scholar, and watch out for exaggerated advertising or absolute claims. If specific paper titles or research results are not mentioned, the scientific basis may be insufficient.

Q4. What is epigenetics? How is it related to dieting?

A. Epigenetics is a phenomenon in which patterns of gene expression change even though the DNA sequence itself does not change. Because environmental factors such as diet, exercise habits, and stress levels can switch genes "on" or "off," even people who are genetically at risk of obesity may be able to suppress that risk through appropriate lifestyle habits. In other words, genes indicate a "tendency" in constitution, not a predetermined destiny.

Q5. Does gut microbiota affect weight management?

A. Yes. Recent research has shown that the composition of gut microbiota affects obesity and energy metabolism. The types and ratios of gut bacteria tend to differ between obese individuals and those of healthy weight, and it is believed that improving the gut environment through dietary fiber intake and consumption of fermented foods can be beneficial for weight management. Because gut microbiota cannot be measured by DNA testing, this is one factor illustrating the limitations of a diet strategy that relies solely on DNA testing.

Q6. Is it possible that dieting using DNA information will become practical in the future?

A. It is possible. The fields of nutrigenomics and precision nutrition are advancing rapidly, and knowledge about the interaction between genes and diet is steadily accumulating. However, before laboratory-level discoveries can be established as an actual consumer-facing service, large-scale clinical trials and reproducibility verification are essential, and this is expected to take considerable time. At present, a scientifically established, well-balanced diet combined with moderate exercise remains the best approach.

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Author

Kihan Tomikin, M.D., Ph.D.

Completed master's and doctoral studies in Biosystem Control and Molecular Information Medicine at the University of Tsukuba
In 2017, developed Japan's first prenatal DNA testing(Patent 7331325) using a proprietary trace-DNA analysis technology(Patent 7121440)

[References]

(1) Genome.gov, 2024
(2) Ministry of Health, Labour and Welfare Scientific Research, 2016
(3) Nature, 2018
(4) JAMA, February 2018