By Dr. Asnat Raziel, bariatric surgeon specializing in obesity treatment, metabolic health and healthy longevity; Director of the Multidisciplinary Center for Obesity Treatment, Assia Medical, Assuta Ramat HaChayal, Tel Aviv
Precision obesity medicine: same BMI, different biology
Precision obesity medicine starts with a simple insight. Two people can walk into the clinic with the same weight, the same BMI and even the same waist size. Yet the reasons they gained weight may be very different. One gets hungry again soon after a meal. Another struggles to recognize fullness. A third eats mainly in response to stress, while a fourth burns relatively little energy.
So today, the key question is not only which drug produces the most weight loss. Rather, it is which medication, which diet and which kind of activity fit the mechanism at work in this particular patient. This is also the basis of a personalized approach to obesity treatment.
The new Mayo Clinic study
In June 2026, Mayo Clinic researchers published a study in the journal Gastroenterology. The team examined 483 adults with obesity. They measured how fast the stomach empties, hunger after a meal and gut hormones. In this way, they identified a subgroup of 130 participants, or 26.9%. Among them, the stomach emptied quickly, hunger after meals was high, and levels of GLP-1, the gut’s fullness hormone, were unexpectedly low.
In addition, this group had low levels of the hormones PYY and CCK. Colon biopsies also showed low expression of the genes that produce GLP-1 and PYY. The most interesting finding came from treatment. After six months of Mounjaro (tirzepatide), patients in this group lost an average of 21.5% of their body weight. By comparison, the other participants lost 11.7%.
It is important to be precise here. Even the Mayo Clinic announcement presents the finding as a first step. The treatment analysis included only 61 patients, and the researchers performed it retrospectively. So this is a promising finding, but not yet a tool for choosing a medication.
Precision obesity medicine: there is still no single test
As of October 2026, no approved blood test, genetic test or algorithm can tell which drug will work best for a given person. For example, researchers can measure GLP-1 after a meal, but this is not a routine test. Hormone levels change quickly and depend on the meal’s makeup and on how the lab handles the sample. A gut biopsy is not suitable for routine care either.
Still, we can already combine tests and questionnaires today. Together, they create a personal profile that helps choose a treatment direction, set goals and track progress.
Classifying obesity by phenotype
One advanced approach is phenotyping, which means classifying patients by the main mechanism that drives their weight gain. In an earlier Mayo Clinic study from 2021, researchers described four phenotypes:
- Hungry Brain: difficulty feeling full during a meal.
- Hungry Gut: fullness fades fast and hunger returns.
- Emotional Hunger: eating in response to stress, sadness or boredom.
- Slow Burn: relatively low energy expenditure.
In that study, choosing a medication by phenotype led to an average weight loss of 15.9% at one year, compared with 9.0% with standard selection. At the same time, 27% of participants had two or more phenotypes. In other words, a phenotype is not a fixed label but a working map.
Questionnaires on hunger, fullness and emotional eating
Structured questionnaires add information that blood tests do not show. They turn feelings into data that we can track over time. Commonly used tools include:
- Three-Factor Eating Questionnaire (TFEQ): uncontrolled eating, emotional eating and restraint.
- Power of Food Scale: how strongly the sight of food, or the thought of it, triggers an urge to eat.
- Binge Eating Scale: identifying signs of binge eating.
- Visual Analogue Scales: ratings of hunger and fullness before and after a meal.
In addition, a short digital diary shows when hunger returns and whether eating came from physical or emotional hunger. If you recognize an emotional pattern in yourself, you will find practical tools in my guide to overcoming emotional eating.
Gastric emptying tests and fullness hormones
A gastric emptying scan is the standard test for measuring how fast a solid meal moves from the stomach into the intestine. The patient eats a meal labeled with a small amount of radioactive tracer, and then undergoes imaging over four hours, according to professional guidelines.
However, guidelines do not recommend this test for every patient before drug treatment. It is expensive, takes time and involves a small radiation dose. Moreover, we lack prospective studies proving that it improves drug selection. Therefore, doctors consider it only in selected cases: severe nausea, vomiting, suspected gastroparesis or hunger that returns especially fast. Likewise, measuring hormones such as GLP-1, PYY and ghrelin remains a research tool for now. You can read background on these hormones in my article on the physiology of satiety.
Metabolism, body composition and blood tests
Indirect calorimetry measures oxygen intake and carbon dioxide output. From these, it calculates RMR, the resting metabolic rate. For someone with a low RMR, it is especially important to preserve muscle, eat enough protein and do strength training. The test does not choose a drug, but it helps identify the Slow Burn phenotype.
A DEXA scan or a high-quality BIA test measures fat mass, muscle mass and belly fat. During treatment with GLP-1 drugs, the goal is to lose fat and keep muscle. So it is worth measuring at the start and again after three to six months. This is one reason body composition matters more than the number on the scale.
Blood tests do not predict drug response, but they are essential for assessing risk. The basic panel includes a blood count, glucose, HbA1c (average blood sugar over three months), kidney and liver function, lipids and TSH. For a broader evaluation, we can add fasting insulin, ApoB, hs-CRP (a marker of inflammation), vitamins and ferritin. On the other hand, there is no justification for a broad hormone panel for everyone without a clear clinical question.
Fitness, sleep and mental health
VO₂max, the maximal oxygen uptake, is an important measure of fitness and of future risk. The most accurate test is an exercise test with gas analysis. Alternatively, you can use a six-minute walk test, a chair-stand test, grip strength and balance. Smart watches and rings do not replace testing, but they are excellent for tracking trends.
In addition, short sleep, sleep apnea, stress, depression and anxiety all disrupt appetite regulation. That is why it helps to add questionnaires such as the PSQI for sleep quality, STOP-BANG for sleep apnea risk, and the PHQ-9 and GAD-7 to screen for depression and anxiety. An abnormal result may change the priorities of treatment.
Longevity questionnaires and Longevity AI
A longevity assessment looks at the ability to live many years with independence and vitality. It covers nutrition, activity, sleep, social ties, cognitive function and falls. For example, we can use the FRAIL Scale for frailty, SARC-F for sarcopenia (muscle loss) risk, and WHO-5 for mental well-being.
A Longevity AI system, meaning artificial intelligence for longevity, can serve as an integration layer on top of all this information. It detects patterns, flags risk factors and sets priorities. However, it does not replace the doctor. Biological age models also differ from one another, so it is best to treat them as tracking tools.
What precision obesity medicine looks like in the clinic
First, the patient fills out digital questionnaires before the visit and shares data from a smart watch. Second, we perform a medical exam, blood pressure, body composition and blood tests. Third, we add RMR, a fitness assessment, sleep monitoring or continuous glucose monitoring as needed. Next, the system combines the data into a personal profile. Finally, we build an integrated plan: medication, nutrition, protein, strength training, sleep and stress management.
Not every test repeats at every visit. We check weight, waist size, hunger and side effects often. In contrast, we assess body composition, RMR and fitness every three to six months. Sometimes a patient loses only a little weight, yet sleeps better, gets stronger and improves blood sugar. That, too, is a meaningful health gain. If you would like a personal assessment, you are welcome to contact my clinic.
What is not ready yet in precision obesity medicine
Commercial microbiome tests cannot currently choose an obesity drug. Similarly, IgG food sensitivity tests are not an accepted tool. In addition, broad genetic tests do not, in most cases, predict which GLP-1 drug will work better. So it is unwise to base a medical decision on a single result.
The bottom line on precision obesity medicine
The Mayo Clinic study is an important step toward precision obesity medicine. It does not yet let us order a simple test and choose a drug based on it. Even so, it shows that treatment response is tied to biology that differs between people. Similarly, the Lancet commission on defining clinical obesity concluded that BMI alone is not enough for personal assessment. Ultimately, the future of precision obesity medicine lies in combining clinical data, questionnaires, body composition, fitness, sleep and artificial intelligence that organizes it all. The goal is broader than weight loss: more healthy years, strong muscles and a good quality of life.
The information in this article is general and does not replace personal medical advice.
References
Study identifies patients with obesity most likely to benefit from GLP-1-based treatment
