New research highlights the powerful impact of endurance cycling on fat distribution and cardiometabolic health, emphasizing fitness over calorie restriction for long-term health benefits.

Study: Effects of 1,144 km of road cycling performed in 7 days: a cardiometabolic imaging study. Image Credit: 24K-Production/Shutterstock.com

In a recent cohort study published in American Journal of Physiology-Endocrinology and Metabolism, researchers investigated the impact of intense cycling on the cardiometabolic profiles, visceral fat, and ectopic fat of middle-aged, male recreational cyclists.

They found that despite increased energy intake, the cyclists experienced a significant decrease in visceral adiposity and fat mass while maintaining high cardiorespiratory fitness.

Background

Regular exercise is known to reduce body fat, even without weight loss, if lean body mass increases. In a notable 2015 study, middle-aged male cyclists biked 2,700 km in 14 days, attempting to match their high energy expenditure with increased energy intake to maintain weight.

While they managed to keep a stable weight, this was misleading regarding body composition; participants lost 2.2 kg of body fat while gaining 2.5 kg fat-free mass. This significant body composition change occurred without imaging to confirm the effects on visceral adiposity and ectopic fat.

The difference in how various fat types respond to large volumes of exercise with minimal weight loss remains unexplored. Therefore, researchers in the present study investigated the effects of a one-week extreme road cycling regimen on body fat distribution using magnetic resonance imaging (MRI).

About the study

The Extreme Exercise and Energy Expenditure (4E) study included 13 healthy male recreational cyclists from Québec City, aged 50 to 66, who were accustomed to long-distance cycling (averaging 5,490 km/year) and had high cardiorespiratory fitness.

The participants were screened based on their ability to maintain an average pace of approximately 30 km/h and were excluded if they were previously competing athletes, had cardiovascular issues, were on certain medications, or had abnormal test results. A total of 11 cyclists completed the study.

Over a week’s duration, the participants cycled 1,144 km on a 104-km loop, with safety measures including police awareness and escort vehicles. Body composition, fat distribution, and cardiometabolic markers were assessed before and after the cycling period using MRI and bioimpedance analysis.

Daily measurements were taken to monitor hydration and body weight, while energy intake was tracked through provided meals and individual food diaries. The cyclists’ data were compared to those of a reference group of 86 asymptomatic healthy males aged 50-66 years who were involved in a separate study on cardiometabolic risk.

Statistical analysis involved the use of post hoc analysis, age-adjusted mixed linear models, Tukey–Kramer post hoc tests, Pearson’s partial correlation coefficients, linear regression analyses, mixed linear models for repeated measures, Student’s t-test, and the Shapiro-Wilk test.

Results and discussion

No significant correlation was found between the participants’ V̇o₂ peak and annual cycling volume. Three participants did not complete the full distance due to exhaustion or mechanical issues, but all reported expected side effects, including muscle fatigue and discomfort.

Despite a minimal average weight loss of 1% and changes in body composition, cyclists showed a significant reduction in visceral adiposity (14.6%) and waist circumference. They maintained a greater energy expenditure than intake on longer cycling days (208 km) compared to shorter ones (104 km), with an overall energy deficit of 6,867 kcal over the week.

Their daily energy intake was higher on longer cycling days, with a macronutrient breakdown indicating a predominant intake of carbohydrates.

Notable improvements were observed in lipid profiles, including a 21.5% reduction in total cholesterol and a 34.6% reduction in non-high-density lipoprotein cholesterol. The cyclists also showed a significant increase in the adiponectin/leptin ratio, indicating improved adipose tissue secretory function. However, no significant changes were found in subcutaneous and cardiac adiposity or liver fat content.

The present study documented, for the first time, the varying changes in subcutaneous, visceral, and ectopic adiposity after participants engaged in an extreme exercise protocol, during which their energy intake was increased to minimize weight loss.

The study is strengthened by its use of gold-standard measurements for body fat distribution and assessment of cardiorespiratory fitness, with detailed documentation of energy intake.

However, energy expenditure was not measured using the double-labeled water method, and the sample was limited to healthy, physically active Caucasian males. The findings need to be confirmed in further studies involving diverse populations, including women.

Conclusion

In conclusion, the seven-day road-cycling experiment with middle-aged recreational cyclists led to a significant reduction in visceral adiposity with minimal weight loss and low liver fat levels.

The findings highlight the necessity of evaluating body composition changes beyond weight loss in endurance exercise interventions and emphasize promoting physical activity over caloric restriction for obesity prevention, especially in today’s environment of readily available, energy-dense processed foods.

While the present exercise protocol may not be feasible for widespread application, it reinforces the idea that humans may be designed for physical activity rather than minimal food intake.