All About Eating: New Studies Give Scientists Valuable Insight into Appetite, Diet, and Metabolism
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One of the best things about the holidays is the food. While you’re busy trying to decide which side dish to bring to the party, researchers are busy making discoveries that change what we thought we knew about food, diet, and how what we eat affects our brains, our health, and our susceptibility to disease.
High-Fat Diet Linked to Stress and Pain
It’s not news that a high-fat diet is bad for your health, but new studies have found more definitive links between high-fat diets and negative effects, including an increase in stress and a heightened reaction to pain.
In a recent study, researchers at Cincinnati Children’s Hospital Medical Center found that putting mice on a high-fat diet created stress in the gut microbiome and affected whole-body metabolism within just 24 hours. By seven days of the same diet, the bodies of the affected mice had adapted to maximize fat absorption.
In a different study, conducted by researchers at the University of Texas at Dallas, mice fed a high-fat diet experienced a neurological change that both transformed acute to chronic pain and made them more likely to experience allodynia—pain from stimuli that do not normally generate a pain response.
Researchers compared the reactions of the high-fat-diet mice with mouse models of both obesity and diabetes, and found that the mice that experienced dietary changes with no underlying disease were uniquely susceptible to allodynia and chronic pain.
One way in which the discovery might help humans is by enabling doctors to recommend dietary changes to prevent the transition from acute to chronic pain, which is a major driver of the opioid epidemic.
Salt, Stress, and Cognitive Decline
The connection between salt and high blood pressure is well known, but a new study of mice at the University of Edinburgh found that a high-salt diet also causes an increase in stress.
When the researchers fed mice a high-salt diet, they saw a 75% increase in resting stress hormone levels, as well as a reaction to environmental stress that was double that of mice fed a low-salt diet. Further studies are planned to determine if there is a connection between a high-salt diet and other behavioral effects, including anxiety and aggression.
Researchers in China are also looking at the effects of a high-salt diet. A new study out of Tsinghua University in Beijing found a connection between high sodium intake and reduced cognitive functioning in older adults in China.
Those results mirror a 2018 mouse study conducted at Weill Cornell Medicine, which found that feeding mice a high-fat diet for 12 weeks caused endothelial dysfunction, reduced blood flow to the brain, and cognitive decline. Interestingly, the blood pressure of the mice was unaffected.
Encouragingly, the cognitive decline appeared to be reversible, either by returning the mice to a normal diet or by using the amino acid L-arginine.
New Clues About Obesity
Many people blame obesity on lifestyle choices, but two new studies show the roots go back much further.
A new study in mice by researchers at the Institute for Biomedical Sciences at Georgia State University found that if a lactating mother consumes a diet lacking fiber, her offspring are more susceptible to becoming obese.
If the mice offspring of the fiber-lacking mother maintained a normal diet after birth, they did not become obese or show any differences in metabolism. However, when put on a high-fat, low-fiber diet that mimics human fast food, the offspring of the fiber-deficient mother gained a significant amount of weight.
If the results translate to humans, it could help explain why some children and adolescents who eat a large amount of fast food gain weight while others don’t.
Another study from the University of Texas Southwestern discovered a cause of obesity in mice that has nothing to do with food.
The UT Southwestern team identified a gene called Ovol2 that, when defective, caused mice to become obese in adulthood regardless of their diet or exercise level. The mice with the mutated gene did not eat excessively, as is the case with other obesity-related genetic mutations, but saw a severe effect on their metabolism.
While an Ovol2 mutation is rare in humans, the research could lead to new treatments for obesity by targeting the function of specific genes.
A Trigger for Binge Eating
Researchers at the California Institute of Technology have uncovered a connection between the role of gut microbiota in mice and the overconsumption of fatty or sweet snacks, even when they have already eaten.
The study examined the role of the gut microbiota in influencing eating behavior, particularly the role antibiotics play in the disruption of bacteria in the gut.
The researchers found that mice whose microbiotas have been disrupted by oral antibiotics ate up to 50% more sugar than mice with normal levels of gut bacteria, but they did not overconsume their normal food.
The team was able to identity two groups of bacteria that were able to curb the overeating when reintroduced into the guts of the mice through fecal transplant—Lactobacillus johnsonii and S24-7.
If the effects can be replicated in humans, it could lead to new treatments for some eating disorders using specific probiotics.
Diet & Disease
Two new studies show a key connection between diet and certain medical conditions.
Researchers at the University of Michigan Rogel Cancer Center found that a low-protein diet could help in the treatment of colon cancer by blocking mTORC1, a regulator that is highly active in certain cancers and can also cause cancer to become treatment-resistant.
A low-protein diet itself would not be enough to treat colon cancer, but it could increase the effectiveness of chemotherapy and other treatments.
A different study, by researchers at the University of Sydney, explored the role of nutrition in the response to infections in mice, and found that diet can have a direct impact on how the body responds to infection.
The researchers fed two groups of mice different diets—one group was fed a grain-based diet, the other was fed an ultra-processed diet low in fiber. The two groups of mice showed no difference in weight gain or metabolic processes—until they were infected with the influenza A virus.
By 10 days after infection, the mice on the grain diet began to gain weight. The mice on the processed diet did not fare as well. Not only did they not gain weight, by 14 days after infection they had all succumbed to the infection.
The researchers concluded that the ultra-processed diet impaired the recovery process, a finding that could have important implications if the effect can be replicated in humans.
‘Tis the season to eat, drink and be merry, but scientific studies offer several reminders that what you eat can affect many aspects of your metabolism, your bodily processes, and your health.