The theme for the 2026 "Lectures by Experts" is "Food." We will explore food from the perspectives of multiple experts. Our guest for the second installment is Associate Professor Kohei Tanizawa (Faculty of Sport Sciences), who specializes in "Health Science." We asked Associate Professor Tanizawa, who conducts research in a wide range of fields from nutrition to physiology, epidemiology, and personalized healthcare, about the role of "food" in our daily "health."
What is the role of "food" when considering health?
Food is the most familiar element related to health. The foundation of daily eating is maintaining a proper energy balance to prevent obesity and being underweight. Incorrect eating habits will inevitably manifest as weight gain or loss. In other words, "weighing yourself every day" is a guideline for considering a good relationship between "health" and "food."
INDEX
▼ "Health science" is about thinking about what we should do to avoid getting sick.
▼ Examining the relationship between dietary patterns and "biological age"
▼The most important thing when measuring your health is "to weigh yourself every day."
"Health science" is about considering what we should do to avoid getting sick.
What kind of research field is "health science," which is Professor Tanizawa's area of expertise?
It's best to think of health science as "the study of how to live a healthy life without getting sick." It researches disease prevention and health promotion from the perspectives of lifestyle habits such as exercise, nutrition, diet, and sleep, as well as psychology and behavior. While clinical medicine specializes in treating diseases, health science has a strong element of preventive medicine.
Since high school, I've been interested in nutrition that contributes to the conditioning and performance enhancement of athletes, so I studied nutrition and exercise physiology at School of Sport Sciences at Waseda University. After that, I went on to graduate school, and with the desire to conduct research that would benefit more people, I shifted my focus to health science.
Books that Professor Tanizawa is currently using for his research
In your research, I often come across keywords such as "physiology," "epidemiology," and "personalized healthcare."
When dealing with the theme of "health," it naturally connects to medical disciplines such as "physiology" and "epidemiology." Furthermore, "personalized healthcare" is a new research area I started as a result of my graduate school research.
First, it's not uncommon to deal with "physiology" in sports science. For example, we use data to examine changes in the function of organs and tissues, such as the mechanism of muscle hypertrophy through strength training or the mechanism by which endurance improves through aerobic exercise, and use physiological knowledge to elucidate how the body responds to and adapts to exercise. In research, we measure physiological indicators such as heart rate and oxygen uptake capacity during exercise and analyze their relationship with athletic performance, which can lead to evidence that a higher oxygen uptake capacity is advantageous for long-distance running.
Epidemiology is the scientific field of study that investigates "how, to what extent, and why" diseases and health problems occur in populations of people. It involves surveys of thousands or tens of thousands of people to statistically clarify the frequency and distribution of diseases and the factors associated with them. As a concrete example, since 2014, we have been working on a project called "WASEDA's Health Study," in which we are conducting an epidemiological survey of 2,000 people.
One example of our research is the "extraction of dietary patterns." Here, we used a dietary questionnaire consisting of 52 food items to conduct a survey, and extracted dietary patterns using a statistical method called "principal component analysis." From the results of this survey, we identified trends such as a "healthy dietary pattern" characterized by high intake of vegetables, mushrooms, seaweed, soy products, fruits, and seafood, and an "alcoholic (evening drinking) dietary pattern" characterized by high intake of alcoholic beverages and seafood. We then examined whether these patterns were associated with a reduction in visceral fat and a rejuvenation of biological age.
A dietary questionnaire consisting of 52 food items was used to extract dietary patterns.
Regarding personalized healthcare, my experience working on genetic research related to aging and longevity at the Tokyo Metropolitan Institute of Gerontology during my graduate studies led me to want to apply genetic knowledge to sports science and health science. One example of personalized healthcare is research on genes related to alcohol metabolism. As you may know, some people are more tolerant to alcohol than others depending on their genetic type, and research has shown that people with a genetic type that makes them less tolerant to alcohol have a higher risk of developing cancer from drinking and therefore need to limit their alcohol consumption. In addition, I am also conducting research that integrates multiple genetic information and lifestyle data to investigate tendencies toward obesity.
From materials created by Professor Tanizawa: It is understood that people with a genetic predisposition to be sensitive to alcohol have a higher risk of developing cancer due to drinking.
This study examines the relationship between dietary patterns and "biological age."
Could you tell me specifically about the research you've been focusing on recently?
As illustrated by the "WASEDA's Health Study" mentioned earlier, one of the research areas we've been focusing on recently is investigating the relationship between dietary patterns and "biological age (degree of bodily aging)." Biological age refers not merely to chronological age, but to "cellular age" estimated from the state of DNA. By measuring "DNA methylation" (*), which is involved in various life phenomena, we can assess how much a person's body is aging.
Analysis of the aforementioned "eating patterns" and their relationship to biological age revealed that among older adults, those with higher scores for "healthy eating patterns" tended to have younger biological ages. This data demonstrates that a healthy diet may slow down the aging process.
* DNA methylation is the process by which small chemical groups called methyl groups bind to specific locations on DNA. Gene function is regulated by DNA methylation.
Please tell me if there's anything students should know about their daily diet.
What I want students to know is that "you don't need to be too fixated on the number of food items." Of course, it would be ideal to eat a variety of foods and have a well-balanced meal at every meal, but it is difficult to maintain such a diet and it is hard to keep it up in the long run. So, instead of having an extremely unbalanced diet, if you have a well-balanced meal with a staple food (rice, bread, etc.), a main dish (meat or fish dish, etc.), and side dishes (salad, stew, etc.) at least once a day, you will not significantly harm your health.
For example, if it's difficult to have a nutritionally balanced breakfast or dinner, ordering a set meal at the school cafeteria for lunch, or adding one or two side dishes to a rice bowl or noodle dish, is perfectly fine. Healthy meals are possible even with eating out or convenience store food if you're creative, so you don't necessarily have to insist on cooking at home. Try to balance your nutrition in a way that suits your own lifestyle and is within your means.
On the other hand, student athletes need to know that in order to increase muscle mass, they need to consume not only protein but also carbohydrates and fats. To increase muscle mass, it is necessary to promote the synthesis of proteins that make up muscles. Proteins are complex molecules made up of many chains of 20 different amino acids. Energy is needed to create complex molecules from simple molecules, and if there is a shortage of carbohydrates and fats, which are the sources of that energy, even if protein is consumed in sufficient quantities, muscle protein synthesis will not be promoted and muscles will not grow. In addition, numerous studies have reported that excessive dietary restrictions for female athletes increase the risk of menstrual irregularities, decreased bone density, and other problems, so caution is necessary.
The most important thing when measuring your health is "to weigh yourself every day."
What does "food" mean to Professor Tanizawa?
Perhaps the most familiar element related to health is "food." However, as a researcher, the more I learn, the more confused I become about the relationship between "health" and "food" (laughs).
When it comes to diet, after much research, I believe we ultimately arrive at a simple approach: prioritizing energy balance. Energy balance refers to the difference between energy (calorie) intake and expenditure. If this balance is zero, there will be no weight gain or loss. Obesity and being underweight, which result from an imbalance in energy balance, are major factors that increase the risk of disease. Therefore, if you can maintain a proper balance between energy intake and expenditure and maintain a healthy weight, most people can maintain good health. Of course, it is also important to eat a variety of foods and strive for a well-balanced diet, but please understand that a proper energy balance is the prerequisite.
Incorrect eating habits will inevitably show up as weight fluctuations. In other words, "weighing yourself every day" is important for re-examining the relationship between your daily health and diet. However, it's also important not to get too caught up in daily weight changes. While overeating or skipping meals can cause your weight to fluctuate by 1-2 kg in a single day, this is mostly due to changes in body water content. To increase or decrease body fat by 1 kg, you need to adjust your energy balance by approximately 7200 kcal. Just a little overeating or skipping a meal won't cause your body fat to increase or decrease by several kg. It's better to observe weight changes over several weeks rather than just a few days.
Finally, please give a message to Waseda students.
Some students may be eating instant noodles for all three meals every day. This may not have a significant impact on your health right now. However, please be aware that the accumulation of lifestyle habits from a young age will greatly affect your health in the future. Of course, it's okay to have days when you eat instant noodles or snacks. On those days, you can adjust your energy balance and nutrient balance on a daily basis by making dinner vegetable-centered or exercising. If adjusting on a daily basis is difficult, you can think about it on a weekly basis. First, start by "weighing yourself every day" and try to be mindful of your energy balance.
Kumpei Tanizawa
Associate Professor Faculty of Sport Sciences. Completed Master's and Doctoral programs at the Graduate Graduate School of Sport Sciences Waseda University. Holds a PhD in Sport Graduate School of Sport Sciences. Specializes in sport science, nutrition, and health sciences.
Courses taught: "Sports Biochemistry and Genetics," "Physical Fitness and Nutritional Science for Health and Sports," etc.
Interview and text: Kenichi Marumo
Photo: Seiji Ishigaki
![[Save version] Map of the four main campuses](https://www.waseda.jp/inst/weekly/assets/uploads/2025/09/17cb2975123fc5103172ef60bd98608d-610x458.jpg)
