Researchers from Bournemouth University collaborated on a large review that examined findings from multiple earlier studies exploring the relationship between diet and mental health. By analyzing the combined data, the team looked for patterns that appeared consistently across different groups of young people. The results were published in the Journal of Human Nutrition and Dietetics.

Mental Health Often Overlooked in Diet Research

“With increasing concern about adolescent nutrition, most public health initiatives have emphasized the physical consequences of poor dietary habits, such as obesity and type-2 diabetes,” said Dr. Chloe Casey, Lecturer in Nutrition and co-author of the study. “However, the mental health implications of diet have been underexplored by comparison, particularly for drinks that are energy dense but low in nutrients,” she added.

Anxiety disorders remain one of the most common mental health challenges among young people. In 2023, an estimated one in five children and adolescents were living with a mental health disorder, and anxiety was among the most frequently reported conditions.

Survey Data Links Sugary Beverages to Anxiety Symptoms

The studies included in the review relied on survey data to measure both sugary drink consumption and mental health symptoms. Drinks high in sugar can include fizzy sodas, energy drinks, sweetened juices, squashes, sweetened tea and coffee, and flavored milks.

Across the research analyzed, the findings pointed in the same direction. Higher consumption of sugary beverages was consistently associated with greater reports of anxiety symptoms in adolescents.

Association Does Not Prove Cause

The researchers stress that the evidence does not show sugary drinks directly cause anxiety. Because the review was based on previously conducted studies, it cannot determine cause and effect.

It is possible that teens who already experience anxiety may consume more sugary drinks. Other shared influences, such as family circumstances or sleep disorders, could also contribute to both increased sugar intake and anxiety symptoms.

“Whilst we may not be able to confirm at this stage what the direct cause is, this study has identified an unhealthy connection between consumption of sugary drinks and anxiety disorders in young people,” Dr. Casey said.

“Anxiety disorders in adolescence have risen sharply in recent years so it is important to identify lifestyle habits which can be changed to reduce the risk of this trend continuing,” she concluded.

The study was led by former Bournemouth University PhD student Dr. Karim Khaled, who now works at Lebanese American University, Beirut.

Obesity remains a major public health concern and is now one of the leading causes of death in high income countries. The World Health Organization reports that adult obesity rates have more than tripled globally since 1975. In 2022, about 2.5 billion adults were overweight, including 890 million who were living with obesity.

At the same time, intermittent fasting has gained enormous popularity. Social media trends, wellness influencers, and claims of fast weight loss and improved metabolism have helped turn fasting into a mainstream strategy.

Review of 22 Clinical Trials Finds No Clear Benefit

To evaluate whether intermittent fasting truly offers an advantage, researchers examined data from 22 randomized clinical trials involving 1,995 adults in North America, Europe, China, Australia, and South America. The studies tested different fasting methods, including alternate-day fasting, periodic fasting, and time-restricted feeding. Most followed participants for up to one year.

When compared with conventional diet advice or no intervention, intermittent fasting did not produce a clinically meaningful difference in weight loss. In practical terms, fasting schedules did not outperform more traditional guidance or doing nothing specific.

Researchers also noted that side effects were not consistently reported across studies, making it difficult to fully assess potential risks. With only 22 trials available, many of them small and uneven in their reporting, the overall evidence base remains limited.

“Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight,” said Luis Garegnani, lead author of the review from the Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre.

Social Media Hype vs Scientific Evidence

Garegnani cautioned that online enthusiasm may be running ahead of the data. “Intermittent fasting may be a reasonable option for some people, but the current evidence doesn’t justify the enthusiasm we see on social media.”

Another concern is the lack of long term research. Few studies have examined how well intermittent fasting works over extended periods. “Obesity is a chronic condition. Short-term trials make it difficult to guide long-term decision-making for patients and clinicians,” Garegnani added.

Most of the trials included primarily white participants from high income countries. Because obesity is increasing rapidly in low and middle income nations, more research is needed in these populations.

The authors emphasize that the findings may not apply equally to everyone. Results could differ based on sex, age, ethnic background, medical conditions, or existing eating disorders or behaviors.

“With the current evidence available, it’s hard to make a general recommendation,” said Eva Madrid, senior author from Cochrane Evidence Synthesis Unit Iberoamerica. “Doctors will need to take a case-by-case approach when advising an overweight adult on losing weight.”

Now, researchers at MIT report evidence that some forms of life may have learned to use oxygen hundreds of millions of years before the GOE. Their findings could represent some of the earliest signs of aerobic respiration on Earth.

In research published in Palaeogeography, Palaeoclimatology, Palaeoecology, MIT geobiologists investigated the origins of a crucial enzyme that allows organisms to consume oxygen. This enzyme is present in most aerobic, oxygen breathing life today. The team determined that it first evolved during the Mesoarchean, a geological era that occurred hundreds of millions of years before the Great Oxidation Event.

Their results may help answer a long standing mystery in Earth’s history. If oxygen producing microbes appeared so early, why did it take so long for oxygen to accumulate in the atmosphere?

Cyanobacteria and Early Oxygen Production

The first known oxygen producers were cyanobacteria. These microbes developed the ability to harness sunlight and water through photosynthesis, releasing oxygen as a byproduct. Scientists estimate that cyanobacteria emerged around 2.9 billion years ago. That means they were likely generating oxygen for hundreds of millions of years before the Great Oxidation Event.

So what happened to all that early oxygen?

Researchers have long suspected that chemical reactions with rocks removed much of it from the environment. The new MIT study suggests living organisms may also have been consuming it.

The team found evidence that certain microbes evolved the oxygen using enzyme long before the GOE. Organisms living near cyanobacteria could have used this enzyme to rapidly consume small amounts of oxygen as it was produced. If so, early life may have slowed the buildup of oxygen in the atmosphere for hundreds of millions of years.

“This does dramatically change the story of aerobic respiration,” says study co-author Fatima Husain, a postdoc in MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS). “Our study adds to this very recently emerging story that life may have used oxygen much earlier than previously thought. It shows us how incredibly innovative life is at all periods in Earth’s history.”

Other co-authors include Gregory Fournier, associate professor of geobiology at MIT, along with Haitao Shang and Stilianos Louca of the University of Oregon.

Tracing the Origins of Aerobic Respiration

This work builds on years of research at MIT aimed at reconstructing the history of oxygen on Earth. Previous studies helped establish that cyanobacteria began producing oxygen around 2.9 billion years ago, while oxygen did not permanently accumulate in the atmosphere until roughly 2.33 billion years ago during the Great Oxidation Event.

For Husain and her colleagues, that long gap raised an important question.

“We know that the microorganisms that produce oxygen were around well before the Great Oxidation Event,” Husain says. “So it was natural to ask, was there any life around at that time that could have been capable of using that oxygen for aerobic respiration?”

If some organisms were already using oxygen, even in small amounts, they might have helped keep atmospheric levels low for a significant stretch of time.

To explore this idea, the researchers focused on heme copper oxygen reductases. These enzymes are essential for aerobic respiration because they convert oxygen into water. They are found in most oxygen breathing organisms today, from bacteria to humans.

“We targeted the core of this enzyme for our analyses because that’s where the reaction with oxygen is actually taking place,” Husain explains.

Mapping Enzymes on the Tree of Life

The team set out to determine when this enzyme first appeared. They identified its genetic sequence and then searched massive genome databases containing millions of species to find matching sequences.

“The hardest part of this work was that we had too much data,” Fournier says. “This enzyme is just everywhere and is present in most modern living organism. So we had to sample and filter the data down to a dataset that was representative of the diversity of modern life and also small enough to do computation with, which is not trivial.”

After narrowing the data to several thousand species, the researchers placed the enzyme sequences onto an evolutionary tree of life. This allowed them to estimate when different branches emerged.

When fossil evidence existed for a particular organism, the scientists used its estimated age to anchor that branch of the tree. By applying multiple fossil based time points, they refined their estimates for when the enzyme evolved.

Their analysis traced the enzyme back to the Mesoarchean, which spanned from 3.2 to 2.8 billion years ago. The researchers believe this is when the enzyme, and the ability to use oxygen, first arose. That timeframe predates the Great Oxidation Event by several hundred million years.

The findings suggest that soon after cyanobacteria began producing oxygen, other organisms evolved the machinery to consume it. Microbes living near cyanobacteria could have quickly absorbed the oxygen being released. In doing so, these early aerobic organisms may have helped prevent oxygen from accumulating in the atmosphere for hundreds of millions of years.

“Considered all together, MIT research has filled in the gaps in our knowledge of how Earth’s oxygenation proceeded,” Husain says. “The puzzle pieces are fitting together and really underscore how life was able to diversify and live in this new, oxygenated world.”

This research was supported, in part, by the Research Corporation for Science Advancement Scialog program.