Medical Bulletin 19/July/2025 - Video

Researchers have conducted the world’s first study to examine the independent effects of dietary cholesterol and saturated fat on low-density lipoprotein (LDL) cholesterol—the so-called "bad" cholesterol.

In this randomized controlled crossover trial, 61 healthy adults with normal LDL cholesterol levels followed three different diets, each for five weeks. One diet was high in cholesterol but low in saturated fat and included two eggs per day. Another was low in cholesterol but high in saturated fat and did not include eggs. The third diet was high in both cholesterol and saturated fat and included only one egg per week. All three diets provided the same amount of calories, and participants rotated through each diet phase. Cholesterol levels were measured at the end of each period.

Their findings revealed that consuming up to two eggs per day, within the context of a high-cholesterol but low-saturated fat diet, can actually help reduce LDL levels and may lower the risk of heart disease.

“In this study, we separated the effects of cholesterol and saturated fat, finding that high dietary cholesterol from eggs, when eaten as part of a low saturated fat diet, does not raise bad cholesterol levels. Instead, it was the saturated fat that was the real driver of cholesterol elevation,” said lead researcher, UniSA’s Professor Jon Buckley.

“You could say we’ve delivered hard-boiled evidence in defence of the humble egg,” he added. “So, when it comes to a cooked breakfast, it’s not the eggs you need to worry about – it’s the extra serve of bacon or the side of sausage that’s more likely to impact your heart health.”

This study not only offers reassurance for egg enthusiasts but also provides a timely reminder to scrutinize the types of fats we consume, rather than placing blame on nutrient-rich foods like eggs.

Reference: Carter, S., Hill, A. M., Yandell, C., Wood, L., Coates, A. M., & Buckley, J. D. (2025). Impact of dietary cholesterol from eggs and saturated fat on LDL cholesterol levels: a randomized cross-over study. The American Journal of Clinical Nutrition.

What Contributes More to Obesity — Poor Diet or Lack of Exercise?

A study published in the journal Proceedings of the National Academy of Sciences (PNAS), reveals that diet — not declining physical activity — is the key driver of rising obesity rates in economically developed countries.

Led by Herman Pontzer, professor in Duke’s Department of Evolutionary Anthropology, the study analyzed data from more than 4,200 adults aged 18 to 60, across 34 populations on six continents. These participants represented a broad range of lifestyles, from hunter-gatherer and farming communities to industrialized societies. The researchers collected extensive measurements of daily energy expenditure, body fat percentage, and body mass index (BMI) to examine how lifestyle and economic development impact energy use and obesity.

To assess the level of industrialization, the team also incorporated the United Nations Human Development Index (HDI), which accounts for factors such as lifespan, education, and economic prosperity. Despite expectations, the study found that people in wealthier countries expend as much — or even more — energy daily than those in less industrialized settings.

“Despite decades of trying to understand the root causes of the obesity crisis in economically developed countries, public health guidance remains stuck with uncertainty as to the relative importance of diet and physical activity. This large, international, collaborative effort allows us to test these competing ideas. It’s clear that changes in diet, not reduced activity, are the main cause of obesity in the U.S. and other developed countries,” said Pontzer.

The researchers emphasize that while diet is the dominant factor in obesity, this doesn’t mean physical activity should be neglected. “Diet and physical activity should be viewed as essential and complementary, rather than interchangeable,” the study notes.

Reference: “Energy expenditure and obesity across the economic spectrum,” Amanda McGrosky et al., Proceedings of the National Academy of Sciences, 14 July 2025 DOI: 10.1073/pnas.2420902122

Insomnia, marked by difficulty falling or staying asleep and early morning awakening, affects 4–22% of the population. It is linked to increased risks of dementia, cardiovascular disease, and other health conditions. While cognitive behavioral therapy is effective, access is often limited due to a shortage of trained therapists, and medications can bring undesirable side effects. To bridge the knowledge gap around the most beneficial forms of exercise for sleep, researchers conducted a large-scale comparative analysis to identify the most effective exercise strategies.

Researchers reviewed randomized controlled trials published up to April 2025 and included 22 studies involving 1,348 adults with insomnia. Participants were assigned to 13 different treatment approaches, including seven types of exercise: yoga; Tai Chi; walking or jogging; strength training; aerobic plus strength training; aerobic combined with therapy; and mixed aerobic activities. The remaining approaches included cognitive behavioral therapy, sleep hygiene, acupuncture/massage, Ayurveda, and standard treatments such as lifestyle changes. These interventions ranged from 4 to 26 weeks.

Validated sleep measures like the Pittsburgh Sleep Quality Index (PSQI) and the Insomnia Severity Index (ISI) were used alongside objective metrics such as sleep efficiency, total sleep time, and time taken to fall asleep.

Tai Chi stood out for its long-term benefits, outperforming other interventions in both subjective and objective sleep measures for up to two years.

The study concludes: “The findings of this study further underscore the therapeutic potential of exercise interventions in the treatment of insomnia, suggesting that their role may extend beyond adjunctive support to serve as viable primary treatment options.” Given their affordability, minimal side effects, and accessibility, these forms of exercise are ideal candidates for integration into mainstream healthcare strategies.

Reference: Zhi-jun Bu, Feng-shuang Liu, Md Shahjalal, Yi-ke Song, Meng-chi Li, Rong-er Zhuo, Qing-hong Zhong, Ya-wen Du, Chen-ge Lu, Zi-han Yang, Han-yu Yang, Pu Zhong, Jian-ping Liu, Zhao-lan Liu. Effects of various exercise interventions in insomnia patients: a systematic review and network meta-analysis. BMJ Evidence-Based Medicine, 2025; bmjebm-2024-113512 DOI: 10.1136/bmjebm-2024-113512

Common Sweeteners Linked to Early Puberty Risk in Children: Study Finds

Consuming certain sweeteners commonly found in processed foods and beverages may significantly increase the risk of early puberty in children, particularly among those with a genetic predisposition, according to research presented at ENDO 2025, the Endocrine Society's annual meeting held in San Francisco, California. The study identified a strong association between the intake of sweeteners such as aspartame, sucralose, glycyrrhizin, and added sugars, and the onset of central precocious puberty — a condition marked by early hormonal and physical changes.

Early puberty, especially central precocious puberty, has become increasingly common in recent years. It can cause emotional and psychological distress, result in shorter adult height, and increase the risk of metabolic and reproductive disorders later in life.

The study drew on data from the Taiwan Pubertal Longitudinal Study (TPLS), which began in 2018 and included 1,407 adolescents. Central precocious puberty was diagnosed in 481 participants. Researchers assessed dietary intake using validated questionnaires and urine tests to measure sweetener exposure. Genetic susceptibility was evaluated using polygenic risk scores derived from 19 genes associated with early puberty. Medical exams, hormone tests, and imaging scans confirmed diagnoses.

The results showed that sucralose was linked to a higher risk of early puberty in boys, while glycyrrhizin, sucralose, and added sugars were associated with increased risk in girls. “This suggests that what children eat and drink, especially products with sweeteners, may have a surprising and powerful impact on their development,” said Yang-Ching Chen, M.D., Ph.D., of Taipei Municipal Wan Fang Hospital and Taipei Medical University.

“The findings are directly relevant to families, pediatricians and public health authorities,” Chen said. “They suggest that screening for genetic risk and moderating sweetener intake could help prevent early puberty and its long-term health consequences. This could lead to new dietary guidelines or risk assessment tools for children, supporting healthier development.”

Reference: https://www.endocrine.org/meetings-and-events/endo-2025