A pair of identical twins followed drastically different diets for 12 weeks to see how their bodies would respond.
One consumed a high-fat, low-carb diet, while the other prioritized carbohydrates. Both became leaner and fitter, but their experiences differed.
Ross and Hugo Turner, British adventurers known for testing fitness and nutrition strategies on themselves, designed the experiment after polling their 25,000 social media followers.
Under the supervision of sports scientists from Loughborough University in the UK, they followed strict eating and exercise plans to explore the effects of macronutrient distribution on strength, fitness, and overall well-being.
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How the Experiment Worked
Both twins maintained a consistent calorie intake of about 3,500 calories per day, split between three meals, two snacks, and a protein shake.
The only difference was how those calories were distributed. Hugo followed a high-fat, low-carb plan, adding extra fats from olive oil, butter, nuts, eggs, and avocados.
Ross, on the other hand, ate a higher proportion of carbohydrates from foods like rice and pasta while minimizing fat intake.
They also followed identical workout routines that included strength training and cardiovascular exercise, resting every three days.
This structure allowed researchers to assess how each diet influenced their strength, endurance, and body composition.
Fat vs. Carbs: How Their Bodies Responded
Both twins saw improvements in their fitness, but their results varied in key ways.
Hugo, who followed the high-fat diet, gained 3 kilograms (6.6 pounds) of muscle and lost 0.3 kilograms (0.6 pounds) of fat.
However, his visceral fat increased slightly from 11.4% to 12.6%. His cholesterol levels remained unchanged, but he reported feeling more fatigued during intense exercise.
“I just never felt good,” he said. “I was eating at least six times a day and never felt full or satisfied.”
Ross, on the high-carb diet, gained 1 kilogram (2.2 pounds) of muscle but lost more fat, dropping 0.9 kilograms (2 pounds).
His visceral fat decreased from 11.5% to 11.1%, and his cholesterol levels improved. Unlike his brother, he felt energized throughout the study.
“Carbs are very good and readily available for providing the body with energy at higher intensities,” he said.
Energy and Endurance Differences
One of the most striking differences between the twins was their endurance performance. Hugo struggled with cardiovascular exercises, particularly during longer sessions.
“Around 40 minutes into the running, I felt like I was completely done. It felt dreadful,” he explained.
Blood lactate testing supported his experience. Researchers measured lactate buildup—an indicator of metabolic effort—during endurance sessions.
Hugo’s results showed he was working harder than Ross to sustain the same level of performance. In contrast, Ross was able to run for longer durations without hitting a wall.
Sports physiologist Steven Harris, who worked with the twins, noted that carbohydrates play a crucial role in endurance performance.
“Generally, if you know you’re going to do a tough training session, you’ll probably perform better if you’ve got some carbs in the tank,” he said.
Challenges of Each Diet
Both twins found their assigned diets restrictive in different ways. Hugo struggled with hunger despite consuming calorie-dense foods.
Since fat has more calories per gram than carbs, portion sizes were smaller, making meals feel less satisfying.
“I was constantly hungry, but equally, I didn’t have the crashes that I would probably associate with a higher-carb diet,” he said.
Ross, while feeling full on a high-carb diet, missed the taste and texture of fatty foods. He occasionally satisfied his cravings with small pieces of dark chocolate but looked forward to reintroducing cheese after the experiment.
“I had my first piece of cheese in 12 weeks yesterday, and it tasted insanely good,” he said.
What This Means for Everyday Nutrition
Although the experiment was anecdotal and not large enough to determine which diet is universally “better,” it highlighted the importance of individual needs and activity levels.
Both twins improved their fitness, but the high-carb diet appeared to support endurance performance better, while the high-fat diet contributed to slightly higher muscle gains.
Harris emphasized that most people should aim for a balanced approach tailored to their lifestyle. “The best diet is one that makes you feel your best and fuels what you need to do,” he said.
For high-intensity activities like running or cycling, carbohydrates may be beneficial. For slower-paced endurance challenges, a higher-fat intake might be more suitable.
The Turner twins plan to apply these insights to future expeditions. When preparing for high-intensity adventures, they’ll prioritize carbohydrates.
For lower-intensity, long-duration activities, they may incorporate more fats.
This experiment reinforces that there is no one-size-fits-all approach to nutrition. Instead, the most effective diet depends on personal goals, activity levels, and how different foods make an individual feel.
