"You Are What You Eat": How the Body Changes with Diet

"You Are What You Eat": How the Body Changes with Diet

What happens to your body when you transition to a plant-based diet? This is a review of the series You Are What You Eat — a unique twin study experiment.

The documentary series You Are What You Eat explores an extraordinary experiment conducted at Stanford University in 2023. For a period of eight weeks, 22 pairs of genetically identical twins followed different diets. One twin in each pair adhered to an omnivorous diet, while the other followed a plant-based diet. The purpose of the experiment was to assess the impact of nutrition on both physical and mental health. The twins' participation made it possible to eliminate the influence of genetic factors and compare the effects of nutrition on human health.

What exactly was analyzed during the experiment?

The scientists aimed to do more than compare diets; they sought to assess the impact of nutrition on various body systems in depth. Participants underwent a comprehensive set of medical tests, and scientists tracked the following key health indicators:

1. Cholesterol levels: Both “bad” LDL cholesterol and “good” HDL cholesterol were measured.
2. Visceral fat: Internal fat was assessed using DEXA scans (dual-energy X-ray absorptiometry).
3. Gut microbiota: The amount of fiber consumed affects the microbiome.
4. Energy and cognitive function: Participants completed questionnaires regarding their well-being, attention span, and mood.
5. Inflammation levels: Markers of chronic inflammation, a major contributor to many diseases, were examined.
6. Biological age: Scientists measured the epigenetic age, which reflects the true state of cells.
7. Sexual arousal: The physiological responses of female participants were tracked using thermographic imaging.

According to the research, it was possible to determine how animal-based and plant-based diets affect the body. Within eight weeks, the study yielded results, which are presented in the series.

Results of the Plant-Based Diet

During the experiment, it became clear that a plant-based diet provides numerous health benefits and improves key health indicators. In particular, the following changes were recorded:

• Reduction of “bad” cholesterol (LDL). All participants in this group experienced a significant reduction in the level of low-density lipoprotein, which is the key factor that causes plaque deposition in blood vessels and increases the risk of cardiovascular disease. This was due to a reduction in the amount of saturated fat and cholesterol in the plant-based diet.
• Those who followed a plant-based diet showed an increase in the number of "good" bacteria, particularly Faecalibacterium prausnitzii. This is linked to the high fiber content of plant foods, as fiber serves as the main source of nutrition for beneficial bacteria. A diverse microbiome not only improves digestion but also enhances immune function.
• Decreased systemic inflammation. Inflammatory markers, including C-reactive protein (CRP), were lower in participants consuming plant-based foods. This finding is especially significant, as chronic inflammation is a known contributor to a wide range of conditions, from diabetes to depression.
• Enhanced cognitive function and increased energy. People on a plant-based diet reported improved well-being, including mental clarity, sustained energy, and emotional stability. These effects may be related to healthier gut microbiota and reduced blood sugar levels.
• An experiment showed a unique result: on a plant-based diet, the body undergoes rejuvenation, as telomeres — the regions at the ends of chromosomes — become longer. Normally, they shorten with age, but this reversal slows down the aging process.
• Improved sexual function in women. Female participants who switched to a plant-based diet exhibited increased measures of sexual arousal. This enhancement is likely due to hormonal balance, improved blood circulation, and reduced inflammation.

In summary, beyond the expected improvements in digestion, the experiment uncovered several additional benefits of plant-based nutrition - notably, biological rejuvenation and enhanced sexual arousal.

Results of the Omnivorous Diet

The impact of the omnivorous diet on the body was controversial, although it was balanced and focused on healthy eating. Over the course of 8 weeks, participants experienced the following changes:

1. Weight gain. Consuming animal protein can support muscle growth when combined with physical activity. However, even with an active lifestyle, muscle gain is typically accompanied by an overall increase in body weight. On average, participants gained 1.8 kg over four weeks.
2. Deterioration of Gut Microbiota. The omnivorous diet was associated with a decline in gut microbial diversity. Due to lower fiber intake, the population of beneficial bacteria decreased — a change that may impair metabolism, weaken the immune system, and increase systemic inflammation.
3. Elevated Inflammatory Markers. Laboratory tests revealed an increase in inflammatory markers, particularly C-reactive protein (CRP). Chronic inflammation is a well-established risk factor for cardiovascular disease, type 2 diabetes, and accelerated aging.
4. Decline in Mental Well-Being. Participants on the omnivorous diet reported decreased concentration and emotional downturns. Compared to the plant-based group, the omnivorous diet appeared to offer less support for psychological health and mood stability.

A separate episode of the series focuses on a scene in which the twins prepare chicken. The kitchen is treated with a special fluorescent marker that makes bacterial spread visible. As a result, we see how potentially dangerous microorganisms spread across all surfaces - including countertops, utensils, and even furniture. This episode demonstrates that raw meat is not just a food item, but a serious source of health hazard. In a home kitchen, it's very easy to trigger this chain of risk. Against this background, plant-based foods are significantly safer and more reliable.

Core Message of the Series

The documentary series You Are What You Eat is based on real scientific research. It does not impose strict dietary rules but presents a data-driven comparison of omnivorous and plant-based diets, allowing viewers to draw their own conclusions.

However, the creators clearly express a preference for plant-based nutrition, as it proved to be the source of numerous positive health changes and improved well-being among participants. In contrast, the omnivorous diet was associated with several negative effects, including a real risk of pathogen transmission from handling raw meat.

It is also important to note that the experiment lasted only eight weeks. Therefore, the conclusions focus on short-term outcomes and do not reflect long-term effects. Still, the unique approach - a parallel study of genetically identical twins following different diets - strengthens the reliability of the results. Scientists from Stanford, UC Berkeley, and the University of Miami have acknowledged the value of this approach. As such, the findings presented in the series offer strong evidence in favor of plant-based nutrition.

Other Fascinating Facts from the Series

1. The body’s reaction to the same foods can vary significantly from person to person. Therefore, the diet should be chosen individually, with close attention to one’s well-being and the effects of specific food components on digestion.
2. Unhealthy diets are the leading risk factor for premature death in the United States. Excessive consumption of processed foods, saturated fats, sugar, and sodium - combined with insufficient intake of vegetables, fruits, whole grains, and healthy fats - is directly associated with high mortality rates in the country.
3. Animal agriculture is a source of approximately 20% of global greenhouse gas emissions, surpassing the emissions of the entire transportation sector, which accounts for around 14%.
4. Cows emit methane during digestion. This greenhouse gas is produced in their stomachs during the fermentation of feed. In terms of its impact on climate change, methane is over 25 times more harmful than carbon dioxide.
5. To switch all cattle to pasture-based systems, agricultural land use would need to increase by 270%.
6. Over 45,000 industrial fishing vessels operate daily, leading to the depletion of ocean resources. At the same time, fish farms generate up to one ton of organic waste per day, which enters surrounding waters and pollutes the environment. Wild salmon often die when passing by such farms due to contact with these waste products. Farm-raised salmon, bred in artificial conditions, typically contain excessive fat, often fall apart during cooking, and have been linked to an increased risk of cancer cell development.
7. In 2021, the acclaimed restaurant Eleven Madison Park made the decision to switch entirely to a vegan menu for environmental reasons. Chef and co-owner Daniel Humm explained that this move was motivated by a desire to reduce the restaurant’s environmental impact and contribute to the fight against climate change. According to Humm, the production of meat and other animal-derived products leaves a significant ecological footprint. As a result, the restaurant’s team reimagined their cuisine around plant-based ingredients, aiming to prove that vegan dishes can be just as elegant, delicious, and innovative as traditional haute cuisine.

Conclusion

You Are What You Eat is far more than a food-based reality show. It is a unique study of the impact of nutrition on the body, showing that dietary choices matter for the heart, brain, gut microbiota, and even mood. The scientific experiment involving 22 pairs of twins not only entertains but also serves as an impetus for change for each viewer.

After all, the series does not contain any categorical conclusions or rigid frameworks. Rather, it includes thorough research and accessible information that anyone can analyze and apply to their own life.

The documentary series is available for viewing at the link below.

You Are What You Eat: A Twin Experiment on Netflix