Twins Follow Vegan and Omnivore Diets—The Unexpected Results Are In, According to Science

21 December 2025

What actually happens when genetically identical twins follow radically different diets—one all plants, one eating everything—while living near-identical lives for three months? The Turner Twins, a pair of 32-year-old British adventurers, decided to turn their own bodies into a scientific battleground between vegan and omnivore diets. The results, scrutinized by researchers at King’s College, may surprise even the most avid nutrition debaters.

The Twin Test: Why Compare Brothers?

With plant-based diets gaining momentum across the globe (and not just on Instagram), the great nutrition debate has become hotter than a vegan chili. But can we truly say which diet is “superior”? Enter Ross and Hugo Turner, identical twins and self-declared “adventure guinea pigs,” who volunteered for the ultimate experiment. One would eat only vegan for twelve weeks (Hugo), while the other stuck to his familiar omnivore plate (Ross). Same genes, same lifestyle, same exercise routines—if there’s ever a situation to fairly pit falafel against filet mignon, this is it.

This rigorous, variables-controlled, twin-study design offered a rare opportunity: see what the real physical and energetic effects of each diet are when just about everything else is the same.

Body Transformations: What Changed—And What Didn’t

Weight and Fat: Hugo, on plants alone, lost 1 kilogram and trimmed his body fat by about 1%. Ross, the omnivore, bulked up with 5 additional kilograms of muscle, but also increased his fat by 2%.
Cholesterol: Hugo’s cholesterol dropped “considerably,” suggesting a heart-health bonus from his vegan fare. Ross’s cholesterol, meanwhile, held steady all the way.

Physically, these results highlight classic contrasts:

The vegan diet encouraged a lighter, leaner body composition alongside apparent cardiovascular benefits.
The omnivore approach proved more effective for building muscle mass, but at the cost of picking up a bit of extra fat.

The message? If you’re yearning for a marathon build, veganism might help you go the distance. Dreaming of starring in a superhero movie? Omnivore menus may get you those biceps—along with a side of extra body fat.

Energy Levels and Day-to-Day Life: Who Felt Better?

Numbers only tell half the story, of course. What the twins felt matters too. Hugo, as a temporary vegan, noticed an increase in his energy during training. The first two weeks were marked by intense cravings for cheese and meat (“who wouldn’t?”), but then his new steady diet of fruit and nuts, along with other plant foods, kept his blood sugar level stable throughout the day. According to Hugo, this resulted in a clearer, more sustained energy.

Ross, still happy with his omnivore meals, gave a somewhat grumpier report. He felt less effective during workouts, never quite reaching peak performance. This unexpected energy lag raises questions about the conventional fear that plant eaters always risk “energy deficiency.” Science—and the Turner Twins—might beg to differ.

Deeper Discoveries: Gut Health and Long-Term Implications

Beyond the bathroom scale and the gym, the study’s biggest bombshell may have landed in the gut. Analysis of Hugo’s microbiome (the buzzing community of bacteria and microbes in the intestines) showed substantial changes after shifting to plant-based proteins. Researchers linked these microbial shifts to increased resistance against chronic issues like obesity and type 2 diabetes. In other words, the vegan diet wasn’t just a heart thing or a waistline thing; it triggered interventions at the very microbial level that may protect long-term health.

This points to a key takeaway: what you eat doesn’t just change how you feel or look, it can recalibrate the health of your entire inner ecosystem—your “barometer” for overall wellbeing, as the researchers described it.

Of course, a science experiment with two adventurous British brothers might not settle the nutrition debate for good. The Turner Twins’ journey is a fascinating snapshot, not a blueprint for everyone. But it does make one thing clear: the vegan vs. omnivore discussion isn’t as black and white as tofu versus steak. Each choice brings its own benefits—leaner body and energy for vegan; strength and muscle gain for omnivore—closely tied to personal health goals. If you take one lesson from the Turner Twins, let it be this: the best diet may simply be the one that works best for you, your genes, and maybe even your gut microbes!