Weight Loss

Posted on Diet, Weight Loss

Keto vs vegan: Study of popular diets finds over fourfold difference in carbon footprints

Keto and paleo diets were found to be the least sustainable -- and have the lowest diet quality scores -- of the six popular diets examined
Keto and paleo diets were found to be the least sustainable — and have the lowest diet quality scores — of the six popular diets examined

This may be tough to swallow for those on keto or paleo diets.

A new study from Tulane University which compared popular diets on both nutritional quality and environmental impact, found that the keto and paleo diets, as eaten by American adults, scored among the lowest on overall nutrition quality and were among the highest on carbon emissions.

The keto diet, which prioritizes high fat and low carbs, was estimated to generate almost 3 kg of carbon dioxide for every 1,000 calories consumed. The paleo diet, which eschews grains and beans in favour of meats, nuts and vegetables, received the next lowest diet quality score and also had a high carbon footprint, at 2.6 kg of carbon dioxide per 1,000 calories.

The study, published in The American Journal of Clinical Nutrition, compiled diet quality scores using data from more than 16,000 adult diets collected by the CDC’s National Health and Nutrition Examination Survey. Individual diets were assigned point values based on the federal Healthy Eating Index and average scores were calculated for those eating each type of diet.

The study’s senior author Diego Rose, professor and nutrition program director at Tulane University School of Public Health and Tropical Medicine, said that while researchers have examined the nutritional impact of keto and paleo diets, this is the first study to measure the carbon footprints of each diet, as consumed by U.S. adults, and compare them to other common diets.

“We suspected the negative climate impacts because they’re meat-centric, but no one had really compared all these diets – as they are chosen by individuals, instead of prescribed by experts – to each other using a common framework,” Rose said.

On the other end of the spectrum, a vegan diet was found to be the least impactful on climate, generating 0.7 kg of carbon dioxide per 1,000 calories consumed, less than a quarter of the impact of the keto diet. The vegan diet was followed by vegetarian and pescatarian diets in increasing impact.

The pescatarian diet scored highest on nutritional quality of the diets analyzed, with vegetarian and vegan diets following behind.

The omnivore diet – the most common diet, represented by 86% of survey participants – sat squarely in the middle of the pack of both quality and sustainability. Based on the findings, if a third of those on omnivore diets began eating a vegetarian diet, on average for any given day, it would be equivalent to eliminating 340 million passenger vehicle miles.

Notably, however, when those on omnivorous diets opted for the plant-forward Mediterranean or fatty meat-limiting DASH diet versions, both carbon footprints and nutritional quality scores improved.

“Climate change is arguably one of the most pressing problems of our time, and a lot of people are interested in moving to a plant- based diet,” Rose said. “Based on our results, that would reduce your footprint and be generally healthy. Our research also shows there’s a way to improve your health and footprint without giving up meat entirely.”

A 2021 United Nations-backed study found that 34% of greenhouse gas emissions come from the food system. The major share of those emissions come from food production, with beef being responsible for 8-10 times more emissions than chicken production and over 20 times more emissions than nut and legume production.

While the environmental impacts of specific foods have been studied extensively, Rose said this study was important because “it considers how individuals select popular diets that are composed of a wide variety of foods.”

Going forward, Rose still has questions about how to encourage eating habits that are better for people and the planet.

“I think the next question is how would different policies affect outcomes and how could those move us toward healthier, more environmentally friendly diets?” Rose said.

Posted on Diet, Weight Loss

How better planning and behaviour regulation may lead to eating less fat

New research suggests coaching overweight or obese pregnant women to improve their ability to plan and progress toward goals may be key to helping them lower the amount of fat in their diet.

Maternal diet quality affects prenatal development and long-term child health outcomes. Still, the stress that typically increases during pregnancy – often heightened by concern for fetal health and anxiety over impending parenthood – may derail efforts to focus on healthful eating, previous research has shown.  

In this new study, researchers at The Ohio State University set out to identify the pathway between stress and total fat consumption, with a broader goal to evaluate an intervention designed to improve the diets of pregnant women who are overweight or obese.

Through a series of questionnaires and statistical analysis, the team found that two thinking-related skills – planning, and execution of those plans – were weakened in women whose stress was high, and those skill gaps were associated with higher total fat intake.

These two skills are known as executive functions, a set of multiple thinking processes that enable people to plan, monitor behavior and execute their goals.

“People with a higher level of stress tend to have a higher intake of fat, too. If stress is high, we’re so stressed out that we’re not thinking about anything – and we don’t care what we eat,” said lead author Mei-Wei Chang, associate professor of nursing at Ohio State.

“That’s why we focused on executive functions as a mediator between stress and diet. And with this baseline data, we have reasons to believe that designing an intervention around executive functions could improve dietary outcomes,” she said. “I would anticipate the results could be similar for nonpregnant women, because it’s all about how people behave.”

The study was published recently in the Journal of Pediatrics, Perinatology and Child Health.

The 70 women enrolled in the study had a pre-pregnancy body mass index of between 25 (scores between 25 and 29.9 are categorized as overweight) and 45 (scores of 30 and higher are categorized as obese).

The participants completed questionnaires assessing both overall perceived stress and pregnancy-related stress, as well as executive functions – specifically focusing on metacognition, or the ability to plan, and behavior regulation, the ability to execute those plans. They also completed two 24-hour dietary recalls of their calorie intake and consumption of total fat, added sugar, and fruits and vegetables.

“We were really interested in the mediation role of executive functions. The mediator is what makes everything happen,” Chang said. “We wanted to know: If we focus an intervention on executive functions, would that carry through to behavior change in dietary intake?

“Weight loss interventions often involve a prescribed diet or meal plan, and you are told to follow it. But that doesn’t lead to behavior change in the long term.”

Statistical modeling showed that higher perceived stress was associated with a worsened ability to plan and monitor behavior, and that pathway was linked to higher total fat intake. Similarly, higher levels of pregnancy-related stress were associated with a lower ability to plan, which in turn was associated with worsened ability to monitor behaviors related to carrying out the plan – and these factors were linked to higher fat consumption.

These pathways suggested that an intervention designed to lower stress would function as a starting point to improve the diet, and enhancing skills through coaching – emphasizing the ability to plan, including being flexible with planning, and behavior monitoring, particularly when making food choices – would be key to changing eating patterns.

“You need to improve executive functions, and you also need to lower stress,” Chang said. She and colleagues are now analyzing data on the effectiveness of an intervention for the study participants that emphasized stress management and boosting executive function to promote healthy eating.

Executive functions are regulated by a specific region of the brain, and strengths or weaknesses in these skill areas are thought to be affected by a variety of physiological factors. Previous research has found that executive function deficits are more likely to occur in women who are overweight or obese than in women whose weight is categorized as normal.

“Executive function is not well-studied, and it is not related to intelligence. But people with low executive function are unable to make detailed plans and stick to them, and that’s how they get into trouble,” Chang said. “Metacognition and behavior regulation must go hand in hand – that way you have a much better chance to control your behaviors, and then you will eat better.”

Posted on Diabetes, Weight Loss

40-year follow-up shows a significant reduction in death rates after bariatric surgery

Study: 40-year follow up shows significant reduction in death rates after bariatric surgery
Study: 40-year follow up shows significant reduction in death rates after bariatric surgery


A new retrospective study with up to 40 years of follow-up shows significant reductions in death rates from all causes and cause-specific conditions such as cardiovascular disease, diabetes and cancer in patients who have undergone bariatric surgery compared to non-surgical participants with severe obesity, according to a new study in Obesity, The Obesity Society’s (TOS) flagship journal.

The study also found evidence suggesting an increased risk of death from chronic liver disease and higher death rates from suicide in younger patients who had bariatric surgery compared to non-surgical participants. The study’s authors observe that the findings of increased suicide rates among younger patients who have had bariatric surgery may promote more aggressive, pre-surgical psychological screening and post-surgery follow-up.

As a result of the decades-long durability of bariatric surgery in reducing death from all causes and decreasing deaths related to cardiovascular disease, diabetes and cancer compared to matched participants, researchers note the findings may not only increase interest in bariatric surgical treatment for patients with severe obesity but, in addition, further, stimulate necessary research related to the discovery of physiologic and biomolecular mechanisms leading to non-surgical treatment that results in weight loss and improved mortality similar to that achieved by bariatric surgery, said Ted D. Adams,

Experts explain that multiple association studies connecting bariatric surgery and mortality outcomes have been reported, predominantly retrospective, with wide variation in study design regarding participant number, control cohorts, mean follow-up, procedure type, age at surgery, clinical endpoints such as life expectancy and death rates for all causes and specific causes, and the presence or absence of prevalent diabetes. The new study builds upon the groups’ reported mortality outcomes following gastric bypass surgery by extending follow-up to 40 years, tripling the number of surgical patients, and using four, instead of one, bariatric surgery procedure.

Researchers used data from the Utah Population Database (UPDB) for the current study. The UPDB includes linked population-based information from Utah with statewide birth and death certificates, driver licenses and ID cards, and voter registration cards. The UPDB creates and maintains links between the database and the medical records held by Utah’s two largest healthcare providers.

Patients who had undergone bariatric surgery in Utah between 1982 and 2018 were identified from three, large bariatric surgical practices in Salt Lake City, Utah, and medical records from the University of Utah and Intermountain Healthcare Enterprise Data Warehouses in Salt Lake City. Non-surgical participants were selected from Utah driver’s license records or ID cards. Because driver’s licenses are generally renewed every five years, multiple records were available for selection to match the bariatric surgeries.

Nearly 22,000 participants with bariatric surgery and without were matched (1:1) for age, sex, body mass index and surgery date with a driver’s license/renewal date. Mortality rates were compared by Cox regression and stratified by sex, surgery type and age at surgery. Whereas mortality after gastric bypass surgery was previously reported from 1984 to 2002, this study extends mortality follow-up through 2021. The four bariatric surgery procedures included Roux-en-Y gastric bypass, adjustable gastric banding, sleeve gastrectomy and biliopancreatic diversion with a duodenal switch.

Results revealed that all-cause mortality was 16% lower in bariatric surgery patients than in non-surgical participants. Lower mortality was observed for both males and females. Mortality after surgery versus non-surgery decreased by 29%, 43% and 72% for cardiovascular disease, cancer and diabetes, respectively. Death rates for males and females from chronic liver disease were 83% higher in patients who had surgery than in non-surgical participants. The hazard ratio for suicide was 2.4 times higher in surgery compared with non-surgery participants, primarily in individuals with ages at the surgery between 18 and 34 years.

“This important study adds to the mounting evidence that bariatric surgery, not only improves the quality of life for patients but will also increase their life expectancy. This work will hopefully improve patients’ access to this effective treatment for obesity, which is still limited to only one per cent of qualified patients. Also, the study highlights the importance of providing more resources for pre-surgical psychological screening and post-surgery follow-up, especially for younger patients,” said Jihad Kudsi.

Posted on Diabetes, Obesity, Weight Loss

Time-restricted eating reshapes gene expression throughout the body.

Science image


Time-restricted eating reshapes gene expression throughout the body. In this illustration, the Ferris wheel displays the interconnected organ systems working smoothly during time-restricted eating, represented by the clock in the middle CREDIT Salk Institute

Numerous studies have shown the health benefits of time-restricted eating, including an increase in life span in laboratory studies, and practices like intermittent fasting, a hot topic in the wellness industry. However, how it affects the body on the molecular level and how those changes interact across multiple organ systems has not been well understood. Now, Salk scientists show in mice how time-restricted eating influences gene expression across more than 22 regions of the body and brain. Gene expression is the process through which genes are activated and responds to their environment by creating proteins.

The findings, published in Cell Metabolism on January 3, 2023, have implications for many health conditions where time-restricted eating has shown potential benefits, including diabetes, heart disease, hypertension, and cancer.

“We found that there is a system-wide, molecular impact of time-restricted eating in mice,” says Professor Satchidananda Panda, senior author and holder of the Rita and Richard Atkinson Chair at Salk. “Our results open the door for looking more closely at how this nutritional intervention activates genes involved in specific diseases, such as cancer.”

For the study, two groups of mice were fed the same high-calorie diet. One group was given free access to food. The other group was restricted to eating within a feeding window of nine hours each day. After seven weeks, tissue samples were collected from 22 organ groups and the brain at different times of the day or night and analyzed for genetic changes. Samples included tissues from the liver, stomach, lungs, heart, adrenal gland, hypothalamus, different parts of the kidney and intestine, and different areas of the brain.

The authors found that 70 per cent of mouse genes respond to time-restricted eating.

“By changing the timing of food, we were able to change the gene expression not just in the gut or in the liver, but also in thousands of genes in the brain,” says Panda. 

Nearly 40 per cent of genes in the adrenal gland, hypothalamus, and pancreas were affected by time-restricted eating. These organs are essential for hormonal regulation. Hormones coordinate functions in different body and brain parts, and hormonal imbalance is implicated in many diseases, from diabetes to stress disorders. The results offer guidance on how time-restricted eating may help manage these diseases.

Interestingly, not all sections of the digestive tract were affected equally. While genes involved in the upper two portions of the small intestine—the duodenum and jejunum—were activated by time-restricted eating, the ileum, at the lower end of the small intestine, was not. This finding could open a new line of research to study how jobs with shiftwork, which disrupt our 24-hour biological clock (called the circadian rhythm) impact digestive diseases and cancers. Previous research by Panda’s team showed that time-restricted eating improved the health of firefighters, who are typically shifting workers.

The researchers also found that time-restricted eating aligned the circadian rhythms of multiple body organs.

“Circadian rhythms are everywhere in every cell,” says Panda. “We found that time-restricted eating synchronized the circadian rhythms to have two major waves: one during fasting and another just after eating. We suspect this allows the body to coordinate different processes.”

Next, Panda’s team will take a closer look at the effects of time-restricted eating on specific conditions or systems implicated in the study, such as atherosclerosis, which is a hardening of the arteries that is often a precursor to heart disease and stroke, as well as chronic kidney disease.

Posted on Diet, Weight Loss

The Green Mediterranean diet reduces twice as much visceral fat as the Mediterranean diet and 10% more than a healthy diet


The green Mediterranean diet (MED) significantly reduces visceral adipose tissue, a type of fat around internal organs that is much more dangerous than the extra “tire” around your waist. The green Mediterranean diet was pitted against the Mediterranean diet and a healthy diet in a large-scale clinical interventional trial- the DIRECT PLUS. Subsequent analysis found that the green Med diet reduced visceral fat by 14%, the Med diet by 7% and the healthy diet by 4.5%. The study was published in BMC Medicine.

Reducing visceral fat is considered the true goal of weight loss as it is a more important indicator than a person’s weight or the circumference of their waist. Visceral fat aggregates over time between organs and produces hormones and poisons linked to heart disease, diabetes, dementia and premature death.

The research was led by Prof. Iris Shaiof Ben-Gurion University of the Negev, Israel, an adjunct Professor from the Harvard School of Public Health, and an Honorary Professor, University of Leipzig, Germany, together with her doctoral student Dr. Hila Zelicha and Italian, German, and American colleagues.

The DIRECT-PLUS trial research team was the first to introduce the concept of the green-Mediterranean diet. This modified MED diet is further enriched with dietary polyphenols and lower in red/processed meat than the traditional healthy MED diet. On top of a daily intake of walnuts (28 grams), the participants consumed 3-4 cups of green tea/day and 100 grams (frozen cubes) of duckweed green shake/day. The aquatic green plant duckweed is high in bioavailable protein, iron, B12, vitamins, minerals, and polyphenols and substituted meat intake.

The team has shown in previous studies that the green MED diet has a variety of salutary effects ranging from the microbiome to age-related degenerative diseases.

Two hundred and ninety four participants took part in the 18-month long trial.

“A healthy lifestyle is a strong basis for any weight loss program. We learned from the results of our experiment that the quality of food is no less important than the number of calories consumed and the goal today is to understand the mechanisms of various nutrients, for example, positive ones such as the polyphenols, and negative ones such as empty carbohydrates and processed red meat, on the pace of fat cell differentiation and their aggregation in the viscera,” says Prof. Shai.

“A 14% reduction in visceral fat is a dramatic achievement for making simple changes to your diet and lifestyle. Weight loss is an important goal only if it is accompanied by impressive results in reducing adipose tissue,” notes Dr. Hila Zelicha.