Beyond Potato Chips and Instant Noodles: Changes in Hormones and Sperm ─ The Invisible Costs of Ultra-Processed Foods

1) "Gaining Weight on the Same Calories, and Affecting Sperm Too"—Key Points of the Latest Study

A research team from Denmark and France conducted a randomized 2×2 crossover study involving 43 healthy young men. They were asked to consume a diet of ultra-processed foods (UPF) and a diet of unprocessed foods for three weeks each. The study thoroughly measured body composition, lipids, hormones, and semen indicators. The results showed that even when calories were matched, the UPF group experienced an increase in fat mass by about 1.4 kg and a worsening of LDL/HDL. Levels of GDF-15 and FSH, which are related to metabolism and reproduction, decreased, and there was a tendency for reduced sperm motility. Additionally, an increase in endocrine disruptors like phthalates was observed, along with a decrease in lithium in blood and semen. The main conclusion of the study is that "the nature of processing itself can be detrimental to health." Cell

2) The Context of "Spermageddon"—Why Male Reproduction is a Topic Now

Since the 1970s, reports have continued that sperm counts worldwide have decreased by about 50% depending on the country, and the media even uses the term "Spermageddon." Multiple factors such as climate, lifestyle, and chemical exposure are involved, but diet is suggested to be a part of it by several studies. This trial is novel in that it confirmed the possibility that the effects of "processing" can appear in humans even in the short term. ZME Science

3) What is UPF—Not Just "What is Added" but "How It's Made"

UPF refers to a group of foods that have undergone advanced industrial processing such as the extensive use of additives, reconstitution, and extrusion (e.g., sweetened beverages, snack foods, processed meats, instant noodles, overly sweet cereals). In the US and UK, it is estimated that about half of total calorie intake comes from UPF. The potential for disruption of metabolism and endocrine systems due to the lack of dietary fiber, fast absorption speed, and chemical contamination from packaging is being discussed. ZME Science

4) "Hypothetical Map" of Mechanisms—Hormones, Pollutants, and Behavior

• Hormonal Axis: The decrease in GDF-15 suggests disruption in appetite and metabolic regulation, and the decrease in FSH raises concerns about its impact on spermatogenesis. There are reports that testosterone may also decrease in the short term, but the focus is on chain changes in multiple hormones. The Washington Post

• Chemical Axis: In the UPF group, phthalates and others increased. Exposure to endocrine disruptors from packaging and processing could affect lipids, hormones, and sperm. Cell

• Nutritional Design Axis: Even with the same calories, differences in food structure (behavior, satiety, gut environment) and matrix breakdown could lead to easier fat accumulation. The short-term increase in fat mass is likely an expression of these complex factors. Cell

5) Study Limitations and Misinterpretation Points

This trial was conducted over 3 weeks×2 conditions and focused on short-term and young men, with a sample size of 43. The reduction in motility was not a "statistically significant large decrease" but rather a "tendency to decrease." Therefore, it is premature to conclude that "UPF immediately 'destroys' sperm." However, the consistent observation of disadvantages under calorie control is significant under a strong causal inference design (crossover). PubMed

6) Media Coverage—Focusing on the "Calorie Myth Shaken"

Major media outlets highlighted the essence of "deterioration even with the same calories," "increase in body fat in a short period," and "increase in chemicals from packaging." French newspapers emphasized the significant changes in three weeks, while American papers detailed that it was a strictly controlled trial involving young men and also mentioned the current state where many countries have UPF intake accounting for 50%. Le Monde.fr

7) Social Media Reactions—A Mix of Enthusiasm, Skepticism, and Practical Discussions

① Spread of Headlines: Headlines like "Gaining Weight and Adverse Effects on Sperm Even with the Same Calories" had strong viral potential, with food information accounts and news outlets posting successively. X (formerly Twitter)

② Skeptics: Criticisms like "N=43 for 3 weeks, caution in generalization" and "only young men" pointed out external validity. Discussions on Reddit continued regarding evidence strength and effect size interpretation. Reddit

③ Mechanism Enthusiasts: Posts from professionals and science communicators focusing on chemicals from packaging and hormonal changes were prominent. X (formerly Twitter)

④ Practical Advocates: Interest gathered around policy and action proposals like "less processed food" and "strengthening labels, taxation, and school meals." The Guardian

⑤ Wave of Secondary Reporting: Numerous mechanical redistributions from science news sites and university releases. SciTechDaily

8) So, What Should We Do?—A Realistic Guide to Avoid "All or Nothing"

• Understand the Baseline of UPF: Visualize how much of your daily meals are "bag, box, or cola" through "photo notes.".

• Replace Just One Meal with "Closer to the Source": Switch to unprocessed foods (fruit + plain yogurt + whole grain bread) for breakfast 5-7 times a week..

• Prioritize Reducing "Liquid Calories" and "Extreme Snacks": They are quickly absorbed and can easily affect metabolism and hormones. The Washington Post

• Focus on "Glass and Metal" for Heating and Storage: Avoid high-temperature contact with plastic containers to reduce the risk of chemicals from packaging. Cell

• Check for "Protein, Fiber, and Short Ingredient Lists" on Labels: These are indicators of processing level.

• Conduct a Short-Term Self-Experiment: For three weeks, reduce UPF by 1-2 items per day and record weight, belt holes, and sense of vitality.

• Let Go of Excessive Guilt: This is also a policy issue. Personal optimization and social rule-making should go hand in hand. The Guardian

9) Conclusion—"Quality of Processing" as the Next Issue

This trial has cast a significant doubt on the era of calorie supremacy. Even with the same amount, the way food is processed may cause people to gain weight, alter hormones, and potentially affect sperm quality. Although the observation period was short, the consistency in direction (body fat ↑, worsening lipid profile, GDF-15/FSH decrease, pollutants ↑, tendency for decreased sperm motility) cannot be ignored. It is time for us to focus not only on **"what we eat" but also "how it is made."** Cell