Tag Archives: metabolism

Metabolism doesn’t change with age — at least not how you think it does

Most of us know the conventional wisdom about metabolism. You put on a few pounds from your 20s onward because the metabolism slows down, especially around middle age. But according to a new study, that’s all wrong.

Image credit: Flickr / Peter Mooney

Using data from 6,500 people ranging from 8 days to 95 years old, researchers from Duke University discovered that there are four very distinct periods of life – as far as metabolism goes. The study also found out that there are no real differences between the metabolism of men and women after controlling for other factors.

“There are lots of physiological changes that come with growing up and getting older,” study co-author Herman Pontzer, associate at Duke University, said in a press statement. “Think puberty, menopause, other phases of life. What’s weird is that the timing of our ‘metabolic life stages’ doesn’t seem to match those typical milestones.”

A new approach to metabolism

Pontzer and a team of scientists analyzed the average calories burned by a group of people as they went about their lives in 29 countries. Previous studies measured how much energy the body uses to perform basic vital functions, such as breathing or digesting. But that only represents 50% to 70% of the calories we burn each day. 

To measure the total daily energy expenditure, the researchers used a urine test known as “doubly labeled water”. It involves having drink water in which the hydrogen and oxygen in the water molecules have been replaced with naturally occurring heavy forms – and then measuring how quickly they are flushed out. 

The technique is considered the most accurate way to measure daily energy expenditure during normal daily life outside of the lab, and its not novel — it has been used since the 1980s but studies have been limited in size and scope due to its cost. That’s why for this new study multiple labs decided to share their data and gather their measurements into a single database. 

“By calculating how much hydrogen you lose per day, and how much oxygen you lose per day, we can calculate how much carbon dioxide your body produces every day,” Pontzer explained. “And that’s a very precise measurement of how many calories you burn every day, because you can’t burn calories without making carbon dioxide.”

The key findings

Energy needs increase during the first 12 months of life, making one-year-old burn calories 50% faster for their body size than an adult, the study showed. And that’s not only because, in their first year, but infants also triple their body weight. Something happens inside a baby’s cells that makes them more active, a process yet unclear to researchers. 

Following this surge in infancy, the data showed that metabolism slows down by 3% every year until we reach our 20s when it levels off into a new normal. Teen years are also a time of growth but the researchers didn’t find any increase in daily calorie needs in adolescence after taking the body size into consideration. But the unexpected findings don’t end there.

Midlife was also very surprising. We used to think that after 30s, it was all downhill when it comes to our weight. But while several factors may explain the thickening waistlines that usually emerge during our working years, the study suggests that metabolism isn’t one of them. In fact, energy expenditures during that period seem to be the most stable.

The findings suggest that our metabolism only tends to slow down after 60. The slowdown is gradual, at only 0.7% a year. But a person in their 90s needs 26% fewer calories each day than someone in midlife. The researchers think lost muscle mass as we get older might be partly to blame, as muscle burns more calories than fat.

“All of this points to the conclusion that tissue metabolism, the work that the cells are doing, is changing over the course of the lifespan in ways we haven’t fully appreciated before,” Pontzer said in a statement. “You really need a big data set like this to get at those questions.”

The study was published in the journal Science. 

Better diets could save billions in U.S. health care costs

Healthier diets could save the US around $50 billion in healthcare costs annually, according to a new study.

Image credits Ylanite Koppens.

Unhealthy diets are a leading cause of poor health, as they promote the development of cardiometabolic diseases (CMDs) such as heart disease, stroke, and type 2 diabetes. A new study led by Brigham and Women’s Hospital researchers estimates that unhealthy diets can account for 45% of all CMD-related deaths in the US, leading to a national healthcare burden of around $50 billion nationally.

Fooding the bill

“There is a lot to be gained in terms of reducing risk and cost associated with heart disease, stroke, and diabetes by making relatively simple changes to one’s diet,” said corresponding author Thomas Gaziano, MD, MSc, of the Division of Cardiovascular Medicine at the Brigham. “Our study indicates that the foods we purchase at the grocery store can have a big impact. I was surprised to see a reduction of as much as 20 percent of the costs associated with these cardiometabolic diseases.”

In collaboration with researchers at the Friedman School of Nutrition Science and Policy at Tufts University, the team looked at the impact of 10 dietary factors — fruits, vegetables, nuts/seeds, whole grains, unprocessed red meats, processed meats, sugar-sweetened beverages, polyunsaturated fats, seafood omega-3 fats, and sodium — on one’s diet on annual CMD-related health costs.

Towards this end, they used data from the National Health and Nutrition Examination Survey (NHANES), to create a representative U.S. population sample of individuals aged between 35 and 85 years old. Then, using a model they developed, the team analyzed how the individual risk of CMDs shift based on the dietary patterns of respondents to the NHANES study. Finally, they calculated what the overall CMD-related costs would be if everyone followed an optimal diet in relation to the 10 factors.

They conclude that suboptimal diets cost around $301 per person per year, for a total of over $50 billion nationally. The team explains that this sum represents 18% of all heart disease, stroke and type 2 diabetes costs in the United States. Costs were highest for those with Medicare ($481/person) and those who were eligible for both Medicare and Medicaid ($536/person).

The consumption of processed meats and low consumption of nuts, seeds, and omega-3 fat foodstuffs (such as seafood) were the highest drivers of CMD risks and additional costs, the team explains.

“We have accumulating evidence […] to support policy changes focused on improving health at a population level. One driver for those changes is identifying the exorbitant economic burden associated with chronic disease caused by our poor diets,” said co-senior author Renata Micha of the Friedman School of Nutrition Science and Policy at Tufts.

“This study provides additional evidence that those costs are unacceptable. While individuals can and do make changes, we need innovative new solutions — incorporating policy makers, the agricultural and food industry, healthcare organizations, and advocacy/non-profit organizations — to implement changes to improve the health of all Americans.”

The results of this study may underestimate the total cost of unhealthy diets, the team explains, as it can contribute to other health complications aside from CMDs. Additionally, other factors beyond the 10 used in this study could drive health risks and costs, they add. Finally, the NHANES study relied on self-reported data — participants were asked to recall what they ate in the past 24 hours — which isn’t very reliable.

The paper “Cardiometabolic disease costs associated with suboptimal diet in the United States: A cost analysis based on a microsimulation model” has been published in the journal PLOS Medicine.

Researchers find out how cells heat themselves

While we knew that mitochondria somehow generate heat, we didn’t exactly understand how. Researchers at the University of Illinois used a tiny thermometer to find out.

The team reports that mitochondria release heat in quick, powerful bursts using energy stored in internal proton batteries. The findings were made possible through the new tool the researchers built, as previous methods were too slow to pick up on the heat spikes.

a) False-color electron microscope image of the probe, scale bar 100 μm. c) A schematic of the experiment. d) Image of the probe in action, scale bar 100 μm.
Image credits Manjunath C. Rajagopal et al., 2019, Communications Biology.

“Producing heat is part of the mitochondria’s role in the center of metabolism activity,” said mechanical science and engineering professor Sanjiv Sinha. “It needs to produce the energy currency that’s used for the activities in the cell, and heat is one of the byproducts.”

Mitochondria also have a mechanism in place to increase heat output if needed, such as when the body’s overall temperature goes down. In order to get a better understanding of how this heat is generated, the team developed a fast-read thermometer probe measure the internal temperature of living cells. Tab of Rhanor Gillette, professor emeritus of molecular and integrative physiology at Illinois, helped test the probe in a mitochondria-rich strain of neurons.

The team then made the cells produce heat. They recorded very fast changes in temperature inside the neurons, “results that were completely different from what has been published before” according to first author Manjunath Rajagopal.

“We saw a sharp temperature spike that is significantly large and short-lived — around 5 degrees Celsius and less than one second,” he explains.

“The gold standard for measuring has been with fluorescence, but it is too slow to see this short, high burst of heat.”

The findings conflict with previous assumptions that mitochondria break down glucose to generate heat: the temperature spikes, Sinha says, are too large. In order to find the source of energy, the team turned to the mitochondria, and chemically induced them to open up protein channels on their membrane.

“In the mitochondria, one part of the glucose metabolism reaction stores some of the energy as a proton battery. It pushes all the protons to one side of a membrane, which creates an energy store,” Rajagopal said.

“We basically short-circuited the stored energy.”

In the future, the team wants to use their probe on other types of cells. One of their primary focus will be identifying therapeutic targets, they add. Better control over this energy sink could have applications against obesity and cancer.

The paper “Transient heat release during induced mitochondrial proton uncoupling” has been published in the journal Communications Biology.

Scientists create artificial material capable of metabolism, self-assembly, movement, and organization — key traits of life

The new material is eerily life-like.

The DNA material is capable of metabolism, in addition to self-assembly and organization. Image credits: John Munson/Cornell University.

What makes something alive? Is it the fact that it has a metabolism, that it can organize itself into a coherent structure? If that’s all it takes, then researchers might have just created artificial life. A Cornell team took advantage of some of DNA’s unique properties to develop a life-like material that can self-organize, self-assemble, and even metabolize nutrients.

“We are introducing a brand-new, lifelike material concept powered by its very own artificial metabolism. We are not making something that’s alive, but we are creating materials that are much more lifelike than have ever been seen before,” said Dan Luo, professor of biological and environmental engineering in the College of Agriculture and Life Sciences.

DNA is the foundation of all life on Earth. It contains the instructions needed for an organism to survive and develop, producing new cells and sweeping old ones away in a hierarchical pattern. However, DNA is also a polymer, meaning it has some useful bio-construction properties that researchers can use.

In this study, Luo and colleagues used what they call DASH (DNA-based Assembly and Synthesis of Hierarchical) materials to create a biomaterial that can autonomously emerge from its nanoscale building blocks and arrange itself — first into simple polymers, then into more complex shapes.

They started from a sequence of 55 nucleotides (the building blocks of DNA and RNA) and from there, the DNA molecules were multiplied hundreds of thousands of times, creating chains of repeating DNA reaching a few millimetres in size. Then, this reaction was injected into a microfluidic device that the necessary energy and materials for biosynthesis.

As material gathered more and more resources, the DNA was able to synthesize new strands at the front end, while the tail end degraded to maintain an optimum balance. Using this mechanism, it was also able to move around, even against the flow — very similar to how slime molds move.

“The designs are still primitive, but they showed a new route to create dynamic machines from biomolecules. We are at a first step of building lifelike robots by artificial metabolism,” said Shogo Hamada, lecturer and research associate in the Luo lab, and lead and co-corresponding author of the paper. “Even from a simple design, we were able to create sophisticated behaviors like racing. Artificial metabolism could open a new frontier in robotics.”

If that wasn’t life-like enough, researchers are currently working on ways to improve longevity and self-replication.

“Dynamic biomaterials powered by artificial metabolism could provide a previously unexplored route to realize “artificial” biological systems with regenerating and self-sustaining characteristics,” the study concludes.

The goal is not to produce artificial life, but rather to use the system as a biosensor or as a dynamic template for making proteins without living cells.

The study was published in Science Robotics.

Hangry man.

Being hungry really does sour your mood, research reveals

That coworker who’ll lay into you if they skipped breakfast? New research suggests his metabolism is partly to blame.

Hangry man.

Image credits Olichel Adamovich.

Researchers from the University of Guelph have shown that a sudden drop in glucose — such as we experience when we’re hungry — can have a dramatic impact on our mood. The findings help explain why so many people bemoan getting “hangry“.

Food fight

“We found evidence that a change in glucose level can have a lasting effect on mood,” said coauthor Francesco Leri, a professor at the university’s Department of Psychology.

“I was skeptical when people would tell me that they get grouchy if they don’t eat, but now I believe it. Hypoglycemia is a strong physiological and psychological stressor.”

For the study, the team worked with a group of lab rats, following their emotional behavior after inducing hypoglycemia (low blood-sugar levels). The group was injected with a glucose metabolism blocker — which artificially induced hypoglycemia — and was placed in a special chamber. The same rats later received an injection of water and were placed in a different chamber.

At the end of the trials, the rats were allowed to enter one of the chambers — and actively avoided the one where they experienced hypoglycemia.

“This type of avoidance behaviour is an expression of stress and anxiety,” said Leri. “The animals are avoiding that chamber because they had a stressful experience there. They don’t want to experience it again.”

The team took blood samples of the rats at various stages during the experiment and report that rats showed higher blood levels of corticosterone, an indicator of physiological stress, following the first step of the trial. In other words, they were likely experiencing acute stress while their blood-sugar levels were artificially lowered to mimic skipping a meal or two.

The rats also appeared more sluggish when given the glucose metabolism blocker. While it may be argued that this effect stems from a lack of glucose in the rats’ systems — muscles use glucose as fuel — the team reports that this doesn’t seem to be the case. When the sluggish rats were given antidepressant medication, “the sluggish behavior was not observed. The animals moved around normally,” Leri explained.

“This is interesting because their muscles still weren’t getting the glucose, yet their behaviour changed.”

“This is interesting because their muscles still weren’t getting the glucose, yet their behaviour changed.”

Overall, the findings support the idea that animals (us humans included) experience anxiety and a sour mood when going hungry for too long. The results may help flesh out our understanding of the treatment dynamic for those who experience anxiety or depression. They may also shed some light on the (still poorly-understood) link between depression and diseases such as obesity, diabetes, and eating disorders.

“When people think about negative mood states and stress, they think about the psychological factors, not necessarily the metabolic factors,” said PhD student Thomas Horman, who led the study. “But we found poor eating behaviour can have an impact.”

“The factors that lead someone to develop depression and anxiety can be different from one person to the next. Knowing that nutrition is a factor, we can include eating habits into possible treatment.”

Next, the team plans to determine whether long-term hypoglycemia may be a risk factor for developing depression-like behavior. While a single missed meal may make us grumpy, doing so constantly may have a dramatic impact on our mood and quality of life:

“Poor mood and poor eating can become a vicious cycle in that if a person isn’t eating properly, they can experience a drop in mood, and this drop in mood can make them not want to eat,” Horman explains.

“If someone is constantly missing meals and constantly experiencing this stressor, the response could affect their emotional state on a more constant level.”

The paper “An exploration of the aversive properties of 2-deoxy-D-glucose in rats” has been published in the journal Psychopharmacology.

Why most diets don’t work

Universal diets don’t work because “healthy food” varies from person to person, a new study has found.

Image via Flickr.

Sadly, only a fraction of all people truly eat healthily these days – we all have our own struggles with food, either because we eat too much, or we eat things that are bad for us, or we don’t have enough money to buy healthy food. But whatever the cause may be, dietary conditions like diabetes are spreading more and more, and by now, it’s clear that dietary policies are inefficient. A new study adds even more complexity to that problem.

Researchers recruited 800 volunteers and had them eat the same thing over a week, testing the blood sugar to see how different people end up metabolizing it. They found that even after eating exactly the same thing, the blood sugar was significantly different from some people to others. This translates to something else: what’s healthy for you may not be healthy for someone else.

“Most dietary recommendations that one can think of are based on one of these grading systems; however, what people didn’t highlight, or maybe they didn’t fully appreciate, is that there are profound differences between individuals – in some cases, individuals have [the?] opposite response to one another, and this is really a big hole in the literature,” said Eran Segal of the Weizmann Institute of Science in Rehovot, Israel.

But it’s not just diets that can be misleading because of this – our entire dietary system may need some tweaking.

“Measuring such a large cohort without any prejudice really enlightened us on how inaccurate we all were about one of the most basic concepts of our existence, which is what we eat and how we integrate nutrition into our daily life”, said Eran Elinav, a co-author of the study. “In contrast to our current practices, tailoring diets to the individual may allow us to utilise nutrition as means of controlling elevated blood sugar levels and its associated medical conditions.”

Monitoring how people’s bodies reacted to regular food was quite surprising; in one case, a middle-aged woman with obesity and pre-diabetes who had long struggled with diets experienced a spike in her blood sugar levels after eating tomatoes: a food that’s really not considered unhealthy.

“For this person, an individualised tailored diet would not have included tomatoes but may have included other ingredients that many of us would not consider healthy, but are in fact healthy for her,” said Elinav. “Before this study was conducted, there is no way that anyone could have provided her with such personalised recommendations, which may substantially impact the progression of her pre-diabetes.”

Indeed, the way to go seems to be personalisation: finding out what works and what doesn’t for each person; however, this doesn’t mean that we shouldn’t believe that “healthy foods” aren’t healthy for us – there’s still a very good chance that they are, but it would definitely help to see how it works for us, personally.

Journal Reference: Cell, Zeevi and Korem et al.: “Personalized nutrition by prediction of glycemic responses”http://dx.doi.org/10.1016/j.cell.2015.11.001



Tricking your body to think it’s fasting might help you live longer and healthier

Fasting has been practiced since ancient times as a cleansing process, often accompanied by prayer and periods of seclusion. Famous enlightened historical figures like Jesus or Buddha are prime examples of such ascetic practice, with the latter almost raising fasting to a form of art.But as a new study has shown, fasting needs not be merely associated with spiritualism or religion – it could very well be a great tool to improve your health.

Several studies have documented the benefits of fasting, but on the other hand how many of us could go through such excruciating torments, living on water alone for days at a time (some Buddhist monks do it for weeks). After all, low calorie diets are hard enough, let alone not eating altogether. A new study, however, suggests that there might be a way to trick your body it’s in fasting mode, and thus reap the benefits, without actually going overboard.


Photo: thedianerehmshow.org

University of Southern California aging researcher Valter Long wanted to see what happened to animals and humans alike if they’d been fed on a fasting-mimicking diet for a couple of days every month. Long and colleagues performed three sets of experiments: on yeast, mice and ultimately humans.

When the yeast was fed with an alternating diet which ranged from a nutrient medium to fasting, the yeast lived longer than the control. Moving on to mice, the researchers offered the rodents a low-protein, low-calorie meal two for a 4-day periods each month. The rest of the month they could eat as much as they pleased. The team found that the fasting mice outlived their control brethren by three months, which is quite a lot considering the lifespan of a mouse. The mice which fed on the fasting-mimicking diet shed fat and were 45% less likely to fall victim to cancer,  blood sugar fell by 40% and the amount of insulin in the blood was 90% lower. This suggests that the fasting helped the mice be less prone to cancer, cardiovascular diseases and diabetes.

The most exciting find was that the low-calorie diet also improved tissue replenishment. Namely, regeneration of the liver was quicker in the fasting animals, and the balance of different types of cells in their blood was more youthful, as echoed by the increase stem cell numbers.

In the experiment on humans, 19 participants were given a box that included powdered soups, nut bars and chips. It provided about 1,090 calories on the first day and about 725 calories on Days 2 through 5. The meals were proportional on a level to the meals served to the fasting mice. Just to get an idea, this is what 200 calories look like. In total, the participants went through only three rounds (5 days every month for three months) of alternating between a fasting-mimicking diet and business as usual.

When compared with the control group, also randomized and comprising 19 participants, the fasting humans showed improved physical condition, less body fat and blood glucose, and lower levels of proteins associated with cardiovascular diseases. Like in the case of the mice, the fasting humans also had more stem cells in their blood. “We think that what the fasting mimicking diet does is rejuvenate,” Longo says. “Everything is getting a little younger and it goes back to working much better,” he added. Longo and colleagues’ findings appeared in the journal Cell Metabolism.

“We try to make it as close as possible to something that looks like normal food,” Longo said, adding that 95% of the dieters stuck with the plan — a success rate that surprised the researchers.

“I think people noticed a lot of results, and that motivated them to come back,” he said.

Longo is now almost ready to wrap up another study featuring 80 to 90 participants and plans on meeting FDA officials to discusses whether the diet might be appropriate for people with illnesses like cancer. Doctors might soon prescribing such diets to patients. However, that doesn’t mean you should try it at home by yourself without any supervision. It can be dangerous, depending on your health history and physical condition. “This is actually a strong intervention,” he warned.


Not enough reasons to give up fatty food? Well, it disrupts your biological clock too!

Eating too much fatty food does not only lead to being overweight and related diseases, but it can also disturb the balance of one’s circadian rhythms, which means your 24-hour biological clock will stop working thee way it should.

Dr. Oren Froy and his colleagues of the Institute of Biochemistry, Food Science and Nutrition at the Hebrew University’s Robert H. Smith Faculty of Agriculture, Food and Environment from Jerusalem found a link between a high-fat diet and disturbances of the biological clock after experimenting on mice.

These disturbances can lead to obesity, psychological and sleep disorders and even cancer because the activity of hormones and enzymes involved in metabolism is affected dramatically.

Even though light is the main factor which influences one’s circadian cycle, diet appears to have a strong effect on it too.

The researchers wanted to find out how important diet is for the way adiponectin works, this being a substance which is highly important for metabolism because it increases fatty acid oxidation and promotes insulin sensitivity.

The mice were fed differently, some with highly-fat food, while others received a low-fat diet. This was followed by a fasting day, while adiponectin activity was verified. The mice who had eaten low-fat food had a normal circadian rhythm of life while the others showed a phase delay as the way proteins involved in fatty acid metabolism worked was affected.

The researchers suggest that eating too much fatty food leads to obesity also because it affects the daily rhythm of clock genes. This may also explain the disruption of other systems connected to metabolic diseases, such as blood pressure levels and the sleep/wake cycle.
Source: The Hebrew University of Jerusalem