A Nutty Way to Curb Cravings


Credit: Wikimedia Commons, Rustedstrings (Roman Oleinik)

Although walnuts are recommended as an effective way to control appetite in people with diabetes, just how they regulate appetite has only recently been discovered. In a new study published in the journal Diabetes, Obesity and Metabolism, researchers examined the brains of 10 obese volunteers who drank breakfast smoothies for five days. Some of the volunteers drank smoothies containing walnuts, while others drank nut-free smoothies that looked and tasted identical. One month later, the participants repeated the study, but this time those who received walnut smoothies during the first trial drank the nut-free beverage and vice versa. Neither the volunteers nor the researchers knew which smoothie the participants consumed during each phase of the study.

At the end of each five-day trial, the volunteers—on an empty stomach—looked at images of “desirable” high-fat foods such as cake and onion rings, healthy foods like fruits and vegetables, and non-edible things like rocks or trees. The people who consumed the walnut smoothies consistently showed more activity in the area of the brain associated with regulating the behavior of eating and feeling satisfied (satiety) when they looked at the high-fat foods. By stimulating this area of the brain called the insula, the researchers think that walnuts promote weight loss by reducing cravings. In fact, the study participants reported feeling less hunger and feeling like they could eat less food after their walnut trial as compared to their nut-free trial.

In addition to reducing food cravings, walnuts are low in saturated fats and high in omega-3 fatty acids and are good sources of fiber and protein. The next time you have the urge to snack, grab a handful of walnuts.


Karen SweazeaKaren Sweazea, PhD, is an associate professor in the School of Nutrition & Health Promotion and the School of Life Sciences at Arizona State University.

A Healthy Diet: A Prescription for a Healthy Life!

food pyramid pie chart

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We have all heard the phrase “You are what you eat.” Not only is there a lot of truth in that little saying, it is also a great reminder for us to be aware of everything we put into our bodies. Everything we eat and drink has an effect on our being and our physical and mental health depends on proper nutrition.

Most people know that nutrition means getting the right amount of nutrients to fuel our bodies and brains. But the difference between the types of nutrients can be less clear.

Nutrients are divided into three categories: micronutrients, macronutrients and water.

Micronutrients are vitamins, minerals and substances such as sodium and potassium called electrolytes. They are essential for growth, development and normal cellular activities. A wide variety of fruits, vegetables and animal products such as meat and dairy are rich in micronutrients.

Macronutrients include carbohydrates (sugar and starches), protein and fats. Macronutrients are extremely important because they give us the calories we need to produce energy. Each person needs a different amount of macronutrients depending on their body size, body composition and level of physical activity. This last point—activity level—is key. We often eat and drink far too many calories for our body’s needs and store the extra calories as fat. The excess fat can become a big problem, causing inflammation, problems with metabolism and cardiovascular issues.

Water is important for maintaining your body’s fluid balance and for functions such as digestion, circulation and body temperature. We also need water to carry nutrients throughout our body and to energize our muscles.

The lack of proper nutrition is still an issue in areas of the U.S. and other Western countries. However, consuming too many calories without enough nutrients is also a critical health problem in the developed world. In fact, the definition of “malnutrition” has been updated to include overnutrition. The expanded definition of malnutrition highlights the serious threat that overnutrition and obesity have on human health.

If you want to learn more about how to fit better nutrition into your life, visit the U.S. Department of Agriculture’s Choose My Plate website. This tool can help jump-start your nutrition knowledge and get you on your way to feeling great.

Audrey Vasauskas


How Obesity Fuels Inactivity


Women jogging in Central Park New York

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More than one in three adults and one in six children in the U.S. are obese. Obesity—defined as a serious degree of overweight—is a leading cause of death, disease and disability. Although obesity has been linked to genetic disorders, it is most often caused by unhealthy behaviors and, therefore, is preventable and reversible.

Throughout the day, we get calories from food and we burn the calories off when we move our bodies. When we eat more calories than we burn, our bodies store the excess calories as fat, which accumulates over time. Eating too many calories and not moving enough are two factors that can cause obesity. Only one in five adults in the U.S. meets minimum physical activity recommendations, making physical inactivity a significant contributor to obesity. People who are overweight need to eat fewer calories and/or increase physical activity to lose excess fat. These lifestyle changes are often challenging, and may be compounded by the fact that exercise may be harder to do when you’re obese.


 The cycle of obesity. Credit: Kim Henige

Carrying excess body weight can make joint pain more likely, which makes physical activity more difficult. Now, researchers may have discovered another reason excess body weight makes physical activity more difficult. A recent study published in the Journal of Applied Physiology shows that the working muscles of obese mice tired out more quickly than those of lean mice. These findings support a cycle of obesity where inactivity leads to obesity, which leads to more inactivity. Breaking the negative cycle of obesity and re-establishing a healthy body weight is possible, but takes considerable dedication and persistence to overcome the barriers and discomfort of the process.

Remember that the path to a healthier weight starts by taking a step! Visit the Centers for Disease Control and Prevention website for weight loss strategies, success stories of people who’ve lost weight and kept it off and more.

Kim HenigeKim Henige, EdD, CSCS, ACSM EP-C, is an associate professor and undergraduate program coordinator in the department of kinesiology at California State University, Northridge.

Handling the Pain of Acid Reflux at Holiday Time

Acid reflux

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With Thanksgiving coming up, eating—of all things rich, indulgent and delicious—is top of mind for many Americans. But for people with gastroesophageal reflux disease (GERD), eating this type of food often and in large quantities can be a challenge. This week is GERD Awareness Week, a good time to learn how to prevent GERD symptoms and still enjoy your holiday season.

GERD is the return of stomach contents, including acid, into the esophagus, sometimes known as acid reflux. More than 60 million people in the U.S. experience GERD symptoms, such as frequent heartburn, at least once a month.

You may have a higher risk of having GERD if you:

  • produce a lot of gastric acid
  • have a hiatal hernia
  • have a weak lower esophageal sphincter (the ring of muscle between the esophagus and stomach)
  • are obese
  • smoke
  • drink alcohol or a lot of caffeine

Women have additional risk factors, including being a young adult and adopting a stooping or slouching posture. Certain foods, including peppermint, chocolate, fatty or fried foods, and acidic fruits, also raise the risk of developing heartburn and acid reflux.

Simple dietary and lifestyle changes can be effective for many people to reduce the frequency and intensity of GERD symptoms, including:

  • losing weight if needed
  • quitting smoking
  • eating small meals throughout the day
  • avoiding foods that cause symptoms
  • waiting at least two hours before lying down after a meal

Another first line of treatment is medication, such as antacids or proton pump inhibitors. These drugs are available over the counter and by prescription from your doctor and reduce or stop the production of stomach acid to prevent symptoms.

If occasional heartburn bothers you after a big meal, try making lifestyle changes to help you feel better. If your symptoms persist, your doctor may look deeper into the possible causes for your discomfort. Knowing the risk factors for GERD can help you avoid complications and stay healthy throughout the holidays and all year long.

To learn more about GERD, visit the National Institute of Diabetes and Digestive and Kidney Diseases website


layla-al-nakkashLayla Al-Nakkash, PhD, is a professor in the Department of Physiology, at Midwestern University, Glendale, Ariz. She is the course director for medical physiology for medical and podiatry students. Her area of research relates to understanding how intestinal dysfunction (in diseases such as cystic fibrosis and diabetes) can be ameliorated by changes in diet.

How Many Hot Dogs Can You Eat in 10 Minutes?

Junk Food

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The competitive-eating elite will descend on New York City’s Coney Island this Fourth of July to flex their hot dog eating skills at the annual Nathan’s Famous Hot Dog Eating Contest. Last year, the male winner ate 62 hot dogs and the female winner ate 38 hot dogs in 10 minutes. Competitive eaters are surprisingly slight for the enormous amount of food they are able to consume. Where do all those hot dogs go?

The stomach is not a passive sack but an active organ that expands and contracts. An empty stomach holds about 1/4 cup, but when a meal is swallowed, the stomach expands to hold as much as 6 cups without stretching its walls. Besides relaxing to hold the meal, the stomach’s walls squeeze in and out and back and forth to move the food into the intestines, a process called gastric emptying. Researchers at the University of Pennsylvania wondered if speed eaters’ ability to keep down so many hot dogs was because their stomachs emptied faster or if their stomachs were trained to hold much more food than the average person.

The researchers recruited a professional speed eater and compared his gastric physiology to an individual with a big appetite. A gastric emptying test revealed that the professional speed eater’s stomach emptied slower than the regular eater. After 10 minutes, the regular eater consumed seven hot dogs, and his stomach was not stretched out. In contrast, the speed eater ate 36 hot dogs, and his stomach became a “massively distended, food-filled sac occupying most of the upper abdomen,” the researchers wrote. While the regular eater felt sick, the speed eater said he didn’t feel full, leading the researchers to wonder if the competitive-eating training made the stomach so stretchy and limp that the competitors never get the “full” physiological signal.

Although the study examined only one professional speed eater, the results support the idea that competitive speed eaters could eat large amounts of food in short periods of time not because their stomachs emptied faster but because their stomachs were able to enlarge dramatically.

The record for most hot dogs eaten is 69. How does the stomach look after that many? Not great, this video from ESPN shows.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.


Does Weight Have to Yo-Yo? Secrets for Keeping Weight Off

Weight scale

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It’s the million-dollar (possibly billion-dollar) weight loss question: How do you keep lost weight off? This question is receiving renewed attention after a recent study reported that most of the contestants on Season 8 of television’s “The Biggest Loser” regained the large amounts of weight they’d lost on the show. Studies in rodents and humans show that soon after dieting or exercising stops, fat rapidly comes back and insulin resistance and glucose tolerance deteriorate. A number of physiological factors contribute to this rebound, including increased appetite and slower metabolism, but new research reports that stress hormones called glucocorticoids may also have a role.

In the study, rats were fed less and ran everyday on a running wheel for three weeks. The rats were then allowed to be sedentary and eat as much food as they wanted. After one week of this relaxed lifestyle, the rats had more fat tissue and worse glucose tolerance and insulin sensitivity than when they were dieting and exercising. But, when given mifepristone—a drug that blocks glucocorticoid hormone activity—during the relaxed week, the rats gained back less weight and their metabolic health didn’t change.

Dieting and exercising is stressful on the body, the researchers wrote, and the stress may prime the body to get back the fat it lost when the dieting and exercising stops. The study finds that glucocorticoid hormones are involved in this process and that preventing their action can reduce weight regain and metabolic changes.

While a miracle pill to keep the weight off may sound like a great solution, the researchers noted that the exercising and dieting rats were still healthier than the rats taking mifepristone. It’s important to emphasize the health benefits of regular exercise and a proper diet, they wrote. While a lifestyle change is the key to keeping weight off, it’s much easier said than done, as the “The Biggest Loser” contestants demonstrate.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

Capsaicin Causes Pain, No Gain

Emily Johnson Capsaicin

William Yang presents “Capsaicin suppresses body weight gain and pain reaction in mice” at the Experimental Biology 2016 meeting in San Diego. Credit: Emily Johnson

Capsaicin is a chemical people love or hate. It’s the chemical in hot peppers and spicy foods responsible for their spicy (and sometimes painful) taste, but researchers in Maryland and Pennsylvania think it may have some health benefits. William Yang, a high school student who worked on the project at the Temple University Lewis Katz School of Medicine in Philadelphia, shared their findings at the Experimental Biology meeting in San Diego.

The research team gave mice capsaicin for a total of 90 days. Mice fed capsaicin gained 16.5 percent less weight than mice in the control group, suggesting that capsaicin either changed their appetite or their body’s metabolism. The mice also showed changes in their ability to handle high blood sugar and high insulin levels, indicating that capsaicin has effects on metabolism.

Yang says future studies are underway in the group’s laboratory to discover how and why these changes happened. In the meantime, the findings tell us that the beneficial effects of eating spicy foods might be worth a little bit of pain.


Emily JohnsonEmily Johnson, PhD, is an APS member and a former volunteer editor for the I Spy Physiology blog.

Is Fat the Sixth Taste?

Chocolate Cake

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Restaurant menus for Valentine’s Day can be described in one word: decadent. From molten chocolate cake to marbled steaks, fat makes these foods so palatable. For a long time, scientists thought that we find heavy foods more appealing because of their mouth feel and aroma. However, recent studies suggest that the tongue might be able to taste fat, along with the five basic tastes—sweet, sour, salty, bitter and umami. This could explain why we are extra perceptive to richness in foods.

As we chew and savor, chemicals released from the food stimulate proteins called taste receptors on the tongue’s taste buds. Each basic taste has dedicated taste receptors, and the basic tastes blend together to give food the flavor we perceive. Contrary to popular belief, the tongue does not have specific regions for each basic taste. Every taste bud has all the taste receptors. How do scientists judge if a flavor is really a basic taste? Many define a basic taste as having all of the following:

  • a source,
  • taste receptors that respond to it,
  • a signaling pathway between the taste receptors and the brain so that we perceive the taste,
  • sensitivity to it that’s controlled by the body, and
  • subsequent effects on the body’s physiology.

So far, the prospect of fat becoming the sixth taste is looking good. Researchers identified the taste source: molecules in fat called fatty acids. They have a few ideas on which receptors fatty acids from fat stimulate, with the strongest evidence supporting a protein called CD36. Along with studies showing that stimulating CD36 sends signals to the brain, other studies have reported that people can tell fattiness without knowing appearance, smell and texture. Certain hormones also appear to control the craving for fat, at least in mice, and there’s evidence that fatty acids on the tongue have physiological effects—they signal to the intestines to get ready to digest fat.

Researchers are also exploring if obesity is related to fat as a taste. Obese mice seem less sensitive to fat and prefer the high-fat chow as a result. People who underwent gastric bypass surgery to treat obesity have said that fatty meals became less appealing after the procedure. More work needs to be done to say conclusively that fat is a basic taste, but imagine eating molten chocolate cake with a dash of “taste of fat” powder. Too decadent?

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

How Our Bodies Turn Food into Energy

Assorted food

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Low carb, high protein, paleo—diet trends often single out a nutrient group as the culprit of unwanted weight gain and an unhealthy lifestyle. But our body needs food for energy, and all three groups—carbohydrates, fats and proteins—have important roles to play. What is energy to the body, and how does the body turn what we’ve eaten into a form it can use?

To the body, energy is a molecule called adenosine triphosphate (ATP). Many of the body’s processes need ATP to happen. For example, for a muscle to contract, ATP needs to be on the muscle cells’ moving parts for the contraction to continue. Rigor mortis, the stiffening of muscles after death, happens because no ATP is around.

Cells have three ways to convert food into ATP: glycolysis, the Krebs cycle and oxidative phosphorylation. Each pathway processes specific nutrient groups: Glycolysis only uses carbohydrates, while the Krebs cycle and oxidative phosphorylation can use all three. In each pathway, the nutrient is broken down in a multi-step process by specialized proteins, and new ATP molecules are regenerated from used ATP along the way. Besides using different transformation steps, the reaction pathways also take place in different parts of the cells. The proteins that carry out glycolysis float throughout the cell, which means glycolysis can happen anywhere. The proteins for the Krebs cycle and oxidative phosphorylation, on the other hand, reside in cell compartments called mitochondria, so these conversions only happen there.

For most cells, glycolysis produces the least amount of ATP. Most of the ATP formation occurs through oxidative phosphorylation and the Krebs cycle. This is why the mitochondria, where these reactions occur, are commonly referred to as the powerhouses of the cell. Both oxidative phosphorylation and the Krebs cycle need oxygen to work, and the Krebs cycle releases carbon dioxide as a byproduct. As a result, most of the oxygen we breathe in goes to the mitochondria for these reactions, and most of the carbon dioxide we’re breathing out comes from them.

What’s the chemistry behind ATP’s energy? Watch this video from Khan Academy for details.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.

A New Meaning for ‘Food Baby’: How the Burmese Python Digests Big Meals

PR Python 3

Credit: Stephen Secor

Thanksgiving dinner can leave the stomach feeling and looking stuffed beyond capacity. The Burmese python goes beyond the post-meal bulge: Its intestines and other organs grow too, and these changes happen within days of eating. A recent study in Physiological Genomics examined how the organs can grow so much so soon.

The Burmese python takes about 10 days to digest its meal.  Within two days of eating, its metabolism and digestive processes are working 10 to 44 times faster. Three days after eating, its heart, liver, small intestines and other organs have grown to up to double in size. The meal is digested by the 10th day after eating, and these bodily changes have reversed. The Burmese python shrinks and returns back to its pre-meal state to go through this cycle again the next time it eats.

A multi-institutional team of researchers led by Todd Castoe, PhD, of the University of Texas at Arlington tracked how gene expression changed as the Burmese python’s body transformed. A gene is expressed when the protein it codes for is made. Greater expression of a gene means more of its protein is produced and present in the body. The researchers found that the expression of at least 2,000 genes changed after the snake ate. To their surprise, most of the shifts occurred soon after eating—within six hours. Genes that varied included those involved with organ structure and nutrient absorption. Gene expression matched and often preceded physiological changes and, like the bodily changes, returned to pre-eating state by the 10th day after eating.

According to the researchers, this study is the first to link the extreme and rapid eating-induced transformations of the Burmese python’s body directly to changes in gene expression and also the first to show how quickly gene expression changed.

Maggie KuoMaggie Kuo, PhD, is the former Communications and Social Media Coordinator for APS. Catch more of her writing in the Careers Section of Science Magazine.