Health
Popular intermittent fasting diets may not deliver the health benefits many expect
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Time-restricted eating has gained popularity in recent years, but a recent study suggests that intermittent fasting — while effective for weight loss — might not live up to the hype in terms of wider benefits.
The small German study found that participants who were placed on two different time-restricted eating schedules lost weight, but experienced no improvement in blood glucose, blood pressure, cholesterol or other key cardiometabolic markers.
The participants included 31 overweight or obese women. One group ate between 8 a.m. and 4 p.m. and the other group ate between 1 p.m. and 9 p.m. for a two-week period, while maintaining their typical caloric intake, according to a press release.
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The findings, which were published in the journal Science Translational Medicine, suggest that the widely touted cardiometabolic benefits of intermittent fasting may be a result of eating fewer calories rather than meal timing, the researchers say.
The participants also showed a shift in their circadian rhythms (sleep/wake cycles) when they were placed on the time-restricted eating schedules, but the associated health impacts are not known.
A recent study suggests that intermittent fasting — while effective for weight loss — might not live up to the hype in terms of wider benefits. (iStock)
The study did have some limitations. Some researchers have cast doubt on the significance of the study due to its small size.
“It is severely underpowered to detect any difference, considering how gentle the intervention is,” Dr. Dr. Jason Fung, a Canadian physician, author and researcher, told Fox News Digital. He also noted that the participants were fasting for 16 hours a day instead of the normal 12 to 14 hours.
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Lauren Harris-Pincus, a registered dietitian nutritionist in New Jersey, agreed that the findings could be due to the fact that there was no intentional caloric restriction, and reiterated that the sample size is “quite small.”
“As a registered dietitian, I only recommend time-restricted eating when it is carefully planned and shifted earlier within the day,” Harris-Pincus, who was not involved in the study, told Fox News Digital.
One group in the study ate between 8 a.m. and 4 p.m. and the other group ate between 1 p.m. and 9 p.m. for a two-week period, while maintaining their typical caloric intake. (iStock)
“Only one in 10 Americans consumes the recommended number of fruits and veggies, and 93% miss the mark on fiber goals. Restricting an eating window necessitates more careful meal planning to ensure adequate intake of macro- and micronutrients.”
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The expert also cautioned that skipping breakfast to enable a later eating window may result in lower intake of the “nutrients of concern” in the American diet, including calcium, potassium, fiber and vitamin D.
Looking ahead, the researchers said more studies are needed to explore the effects of time-restricted eating over longer time periods. It also remains to be seen how the combination of caloric restriction and time-restricted eating may affect outcomes. Future research could also explore how different populations may respond.
“I only recommend time-restricted eating when it is carefully planned and shifted earlier within the day.”
Dr. Daryl Gioffre, a gut health specialist and celebrity nutritionist in New York, noted that the study didn’t account for critical factors like chronic stress, sleep quality, medications, hormone status and baseline metabolic health.
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“All of these can significantly blunt fat loss and cardiometabolic improvements,” Gioffre, who also was not involved in the research, told Fox News Digital.
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“Cortisol, the body’s primary stress hormone, is naturally highest in the morning, which overlaps with one of the fasting windows studied,” he went on. “If stress is elevated, cortisol alone can block fat burning, disrupt blood sugar regulation, and mask cardiovascular improvements, regardless of calorie intake or eating window.”
Growing research shows intermittent fasting — when done correctly and sustained over time — can improve insulin regulation, reduce inflammation, support fat loss and contribute to better cardiovascular health, an expert said. (iStock)
Gioffre did agree, however, that growing research shows intermittent fasting — when done correctly and sustained over time — can improve insulin regulation, reduce inflammation, support fat loss and contribute to better cardiovascular health.
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“These are outcomes that simply cannot be captured in a short, stress-blind study like this,” he added.
Fox News Digital reached out to the researchers for comment.
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Health
One common type of fat may increase diabetes risk, while another helps fight it
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A new review suggests that the type of fat you eat may affect your risk of developing type 2 diabetes.
Saturated fats rich in palmitic acid – the most common saturated fatty acid in U.S. foods – appear to make it harder for the body to respond to insulin.
Meanwhile, monounsaturated fats rich in oleic acid — such as those found in olive oil — may help protect against insulin resistance, the review concluded.
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“Palmitic acid is found in meats, dairy products, cocoa butter and in the form of palm oil in foods, including margarine, cereal, sweets, baked goods and fast foods,” Tanya Freirich, a registered dietitian nutritionist in Charlotte, North Carolina, told Fox News Digital. She was not involved in the review.
“Oleic acid, on the other hand, is in higher concentration in foods like olive oil, canola oil, nuts, sunflower seeds, eggs, olive, avocados and also in meats (beef, chicken, pork), milk, cheese and pasta.”
Saturated fats rich in palmitic acid – the most common saturated fatty acid in U.S. foods – appear to make it harder for the body to respond to insulin. (iStock)
The review, which was published in the journal Trends in Endocrinology & Metabolism, was led by researchers from the University of Barcelona and the CIBER Area for Diabetes and Associated Metabolic Diseases (CIBERDEM) in Spain.
The findings suggest that fat quality may be more important than total fat quantity when it comes to metabolic health and diabetes risk.
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This appears to support the idea that diets rich in monounsaturated fats, such as the Mediterranean diet, may contribute to lower rates of type 2 diabetes.
“Palmitic acid promotes several molecular processes that impair insulin action,” study investigator Dr. Manuel Vázquez-Carrera, from the Department of Pharmacology, Toxicology and Therapeutic Chemistry at the University of Barcelona, told Fox News Digital.
“Palmitic acid is found in meats, dairy products, cocoa butter and in the form of palm oil in foods, including margarine, cereal, sweets, baked goods and fast foods,” a nutritionist said. (iStock)
Too much palmitic acid can cause harmful fat byproducts to build up in the body, which can impair the body’s ability to respond to insulin, he warned. This makes it harder to control blood sugar and increases the risk of insulin resistance and type 2 diabetes.
“It also promotes inflammation, oxidative stress, mitochondrial dysfunction and cellular stress responses, which contribute to insulin resistance and β-cell dysfunction,” Vázquez-Carrera added.
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By contrast, oleic acid – a hallmark of the Mediterranean diet – does not have these harmful effects, according to the researcher.
“In fact, oleic acid can counteract many of the detrimental effects triggered by palmitic acid, by promoting the storage of fatty acids in relatively inert triglycerides, preserving mitochondrial function and reducing inflammation,” he said.
“All sources of fat in our diet contain a mix of saturated and unsaturated fatty acids.”
Freirich confirmed that the review is consistent with previous research supporting the use of olive oil in the diet for metabolic benefits.
“Also confirming previous research, the consumption of saturated fats is associated with some negative metabolic changes,” she told Fox News Digital.
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Given the complexity of foods and diets, there is an overlap between foods that contain both types of fatty acids, the nutritionist noted.
“Palmitic acid and oleic acid can both be found in olive oil, baked goods and fast foods, in differing amounts,” she said. “All sources of fat in our diet contain a mix of saturated and unsaturated fatty acids.”
Study limitations
Vázquez-Carrera noted that these findings come from a review of numerous experimental, clinical and epidemiological studies rather than a single clinical trial.
“One important limitation is that much of the mechanistic evidence comes from cell culture and animal studies,” he said.
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“Although these studies provide valuable insights into how specific fatty acids affect insulin signaling, further human intervention studies are needed to confirm the extent to which these mechanisms operate in everyday dietary settings.”
In addition, many of the human studies in the review relied on self-reported dietary intake, which can introduce inaccuracies.
Type 2 diabetes develops over many years, with genetics, lifestyle and environmental factors all playing a role, the researcher noted. (iStock)
“Another challenge is that people consume foods containing complex mixtures of fatty acids and bioactive compounds rather than isolated fatty acids,” Vázquez-Carrera added. “Therefore, it remains difficult to fully disentangle the specific contribution of individual fatty acids in free-living populations.”
Nutritional recommendations
The review’s findings appear to support current dietary recommendations that emphasize replacing part of the saturated fat intake with unsaturated fats, according to Vázquez-Carrera.
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“This means favoring dietary patterns rich in foods such as extra-virgin olive oil, nuts, seeds, legumes, vegetables, fruits and fish, while limiting excessive consumption of foods rich in saturated fats, especially highly processed foods,” he advised.
The review does not suggest that a single nutrient alone determines diabetes risk, the researcher pointed out.
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“Rather, maintaining a healthy body weight, engaging in regular physical activity and following an overall healthy dietary pattern, such as the Mediterranean diet, remain fundamental strategies for preventing insulin resistance and type 2 diabetes.”
Type 2 diabetes develops over many years, with genetics, lifestyle and environmental factors all playing a role, Vázquez-Carrera noted.
Improving the quality of dietary fat intake could prove to be an effective strategy for reducing type 2 diabetes risk, the review suggests. (iStock)
“Future research should move beyond simply classifying fats as ‘good’ or ‘bad’ and instead focus on understanding how specific fatty acids, their dietary sources and their interactions within whole dietary patterns affect metabolic health,” he said.
Improving the quality of dietary fat intake could prove to be an effective strategy for reducing type 2 diabetes risk, according to the researcher.
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“A simple takeaway for consumers is to swap out foods high in saturated fat more often with foods rich in heart-healthy fats, like olive oil, nuts and avocados, to better support blood sugar and metabolic health,” advised New Jersey-based registered dietitian Erin Palinski-Wade, who was also not involved in the review.
Anyone at a higher risk for type 2 diabetes should consult a healthcare provider for personalized guidance on nutrition, exercise and other preventive measures, experts say.
Health
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