New Evidence Strengthens the Link Between Hypothalamic Injury, Obesity, and Insulin Resistance

Obesity involves changes in the function of brain regions that regulate body fatness and blood glucose, particularly a region called the hypothalamus.  My colleagues and I previously showed that obesity is associated with inflammation and injury of the hypothalamus in rodent models, and we also presented preliminary evidence that the same might be true in humans.  In our latest paper, we confirm this association, and show that hypothalamic injury is also associated with a marker of insulin resistance, independently of BMI.

Introduction

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Fat, Added Fat, and Obesity in America

In the last post, we saw that carbohydrate and particularly sugar intake have been declining in the US since 1999, even as our obesity rate has continued to climb.

In this post, let's look at another putative driver of obesity: our fat intake, and especially our intake of added fats like seed oils, butter, and olive oil.  Like the graphs in the last post, the data underlying the following graphs come from USDA food disappearance records (not self-reported), and NHANES survey data (1, 2).  Also like the last post, the graph of total fat intake is not adjusted for waste (non-eaten food), while the graph of added fat intake is*.  As a consequence, the figures for total carbohydrate and total fat intake are higher than actual intakes, but still good for illustrating trends.

Here we go.  First, total fat:
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Carbohydrate, Sugar, and Obesity in America

We like explanations that are simple, easy to understand, and explain everything.  One example of this is the idea that eating carbohydrate, or sugar, is the primary cause of obesity.  This lets us point our finger at something concrete and change our behavior accordingly.  And it's true enough that it has practical value.  But the world around us often turns out to be more complex than we'd like it to be.

The CDC recently released its latest data on the prevalence of obesity in the US, spanning the years 2013-2014 (1).  These data come from its periodic National Health and Nutrition Examination Surveys (NHANES).  Contrary to what many of us had hoped for after a slight decline in obesity in the last survey, the prevalence has once again increased.  Today, roughly 38 percent of US adults have obesity.  As a nation, we're continuing to gain fat, which is extremely concerning.

I decided to examine the relationship between obesity prevalence and our intake of carbohydrate and sugar over the years.  The food intake data come from the USDA's Economic Research Service (2).  For some reason, the data on carbohydrate don't extend beyond 2010.  This probably relates to funding cuts at the USDA*.

Let's have a look at the data for carbohydrate:

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Food Reward Friday

This week's lucky "winner"... the Reese's PBC Burger!!

Image credit: The Works

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Do Processed and Red Meat Cause Cancer?

Today, the World Health Organization's International Agency for Research on Cancer published a statement in The Lancet detailing its position on the carcinogenicity of processed and red meat (1).  The statement, resulting from a meeting of 22 scientists from 10 countries, concluded that processed meat is a group 1 carcinogen, meaning that it is "definitely carcinogenic to humans".  They also judged that red meat is a group 2A carcinogen, meaning that it probably causes cancer but the evidence isn't as strong.  They're mostly referring to the links between processed and red meat and digestive tract cancer, particularly cancers of the colon and rectum.

These statements were met with a media frenzy, and the expected furor from the meat industry.  The most surprising thing, for me, is that anyone would be surprised by the IARC's statement.

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Why Do Girls and Boys Reach Puberty Younger Than They Used To?

Girls, and probably boys, are reaching puberty years younger than they did in our great-grandparents' generation.  Why?  There's no shortage of explanations, but the primary reason is probably quite simple.

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11 Basic Guidelines for General Health and Longevity Infographic

8 Summer Steps for Healthy Living

In the warmer, longer, lazier days of summer, the living may not be easy, but your life probably feels less chaotic. Even adults tend to adopt a "school's out!" attitude in summer. That's why this is a perfect time to improve your health in a fashion so seasonally laid back you'll barely notice the effort.

To get you started, WebMD went to eight health experts in fields such as diet, fitness, stress, vision, and oral health. We asked them this: If you could only suggest one simple change this season to boost personal health, what would it be? Here are their top eight tips.

1. Give Your Diet a Berry Boost
If you do one thing this summer to improve your diet, have a cup of mixed fresh berries -- blackberries, blueberries, or strawberries -- every day. They'll help you load up on antioxidants, which may help prevent damage to tissues and reduce the risks of age-related illnesses. Blueberries and blackberries are especially antioxidant-rich.

A big bonus: Berries are also tops in fiber, which helps keep cholesterol low and may even help prevent some cancers.


2. Get Dirty -- and Stress Less
To improve your stress level, plant a small garden, cultivate a flower box, or if space is really limited, plant a few flower pots -- indoors or out.

Just putting your hands in soil is "grounding." And when life feels like you're moving so fast your feet are barely touching the stuff, being mentally grounded can help relieve physical and mental stress.

3. Floss Daily
You know you need to, now it's time to start: floss every single day. Do it at the beach (in a secluded spot), while reading on your patio, or when watching TV -- and the task will breeze by.

Flossing reduces oral bacteria, which improves overall body health, and if oral bacteria is low, your body has more resources to fight bacteria elsewhere. Floss daily and you're doing better than at least 85% of people.

4. Get Outside to Exercise
Pick one outdoor activity -- going on a hike, taking a nature walk, playing games such as tag with your kids, cycling, roller blading, or swimming -- to shed that cooped-up feeling of gym workouts.

And remember, the family that plays together not only gets fit together -- it's also a great way to create bonding time.

5. Be Good to Your Eyes

To protect your vision at work and at play, wear protective eyewear. When outdoors, wear sunglasses that block at least 99% of ultraviolet A and B rays. Sunglasses can help prevent cataracts, as well as wrinklesaround the eyes.

And when playing sports or doing tasks such as mowing the lawn, wear protective eyewear. Ask your eye doctor about the best type; some are sport-specific.

6. Vacation Time!

Improve your heart health: take advantage of summer's slower schedule by using your vacation time to unwind.

Vacations have multiple benefits: They can help lower your blood pressure, heart rate, and stress hormones such as cortisol, which contributes to a widening waist and an increased risk of heart disease.

7. Alcohol: Go Lite

Summer's a great time to skip drinks with hard alcohol and choose a light, chilled alcoholic beverage (unless you are pregnant or should not drink for health or other reasons).

A sangria (table wine diluted with juice), a cold beer, or a wine spritzer are all refreshing but light. In moderation -- defined as one to two drinks daily -- alcohol can protect against heart disease.

8. Sleep Well

Resist the urge to stay up later during long summer days. Instead pay attention to good sleep hygiene by keeping the same bedtime and wake-up schedule and not drinking alcohol within three hours ofbedtime.

It's also a good idea to avoid naps during the day unless you take them every day at the same time, for the same amount of time.

There they are: Eight super simple ways to boost your health this summer. Try one or try them all. They're so easy you won't even know they're -- shhhh -- good for you.

Will You Fill Out This Paleo Diet Survey?

This week, I received an e-mail from a graduate student at Humboldt State University named May Patiño.  She asked me to share her online research survey targeted to Paleo dieters.  Here are the goals of her research, in her words:

The main objective of my study is exploring how the Paleo diet is being implemented in practice.  I would like to assess the health outcomes of these practices, as well evaluate how closely they conform to, or deviate from ways this diet is being described in theoretical literature, and implemented in controlled diet trials. I also want to be able to use the data collected to help explain what is driving the popularity of the ancestral health movement. Ultimately, I would like this information to be used to better inform protocols for controlled diet trails.

The survey took me about 40 minutes to complete.  You're welcome to participate whether or not you're on the Paleo diet.  Please consider taking the survey, for the love of science!

Research Survey: The Paleo Diet in the US

That Time I Ate Most of a Large Pizza in One Sitting

Two weeks ago, I had a brush with Extreme Eating.  My experience illustrates some important principles of how the brain regulates appetite and body fatness-- and how it reacts to calorie-dense, highly rewarding foods.


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Out for Two Weeks

I'll be out of town with limited internet until September 27th.  Feel free to leave comments, but I won't be able to moderate them until I return.  Sorry for the inconvenience!

How Much Does Sugar Contribute to Obesity?

Last week, the British Medical Journal published a review article titled "Dietary Sugars and Body Weight", concluding that "free sugars" and sugar-sweetened beverages contribute to weight gain.  But what are "free sugars", and why does the scientific literature suggest that the relationship between sugar intake and body weight isn't as straightforward as it may initially appear?

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More Thoughts on the Recent Low-fat vs. Low-carb Metabolic Ward Study

The recent low-carb vs. low-fat study has provoked criticism from parts of the diet-health community.  Let's examine these objections and see how they hold up to scientific scrutiny.
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A New Human Trial Undermines the Carbohydrate-insulin Hypothesis of Obesity, Again

The carbohydrate-insulin hypothesis of obesity states that carbohydrates (particularly refined carbohydrates and sugar) are the primary cause of obesity due to their ability to increase circulating insulin, and that the solution to obesity is to restrict carbohydrate intake.  Numerous studies have tested this hypothesis, more or less directly, in animals and humans.  Despite the fact that many of these studies undermine the hypothesis, it remains extremely popular, both in the popular media and to a lesser extent among researchers.  A new human trial by Kevin Hall's research team at the US National Institutes of Health offers very strong evidence that the carbohydrate-insulin hypothesis of obesity is incorrect.  At the same time, it offers surprising and provocative results that challenge prevailing ideas about diet and weight loss.

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Refined Sugar Worsens Blood Lipid Markers of Cardiovascular Disease

Blood lipids such as LDL and HDL cholesterol are markers of the biological processes that impact cardiovascular disease, and they are commonly measured to assess cardiovascular risk.  When we think about the impact of food on blood lipids, dietary fat typically comes to mind.  Yet a new study shows that dietary carbohydrate, specifically high-fructose corn syrup, can have a large impact on blood lipid markers of cardiovascular disease risk.

Introduction

Dietary fats have well-established impacts on blood lipids.  For example, in short-term feeding trials, saturated fat tends to increase total cholesterol, increase LDL ("bad") cholesterol, and increase HDL ("good") cholesterol, while the omega-6 polyunsaturated fat linoleic acid decreases total cholesterol and decreases LDL cholesterol.  For this reason, dietary advice to reduce cardiovascular risk tends to focus on dietary fat.

The hypothesis that refined dietary sugar is harmful to the cardiovascular system isn't new.  In 1972, British physiologist and nutrition researcher John Yudkin published a classic book called Pure, White, and Deadly, which argued, among other things, that refined sugar is harmful to the cardiovascular system.  Yet at the time, the supporting data were weak, and the hypothesis was never taken very seriously by the scientific community.

Peter Havel and his group at UC Davis have begun to breathe new life into this hypothesis with their rigorous work on the cardiovascular effects of dietary sugars.

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What Properties Make a Food "Addictive"?

Although the concept of food addiction remains controversial, there's no doubt that specific foods can provoke addiction-like behaviors in susceptible people.  Yet not all foods have this effect, suggesting that it's related to specific food properties.  A new study aims to identify the properties that make a food "addictive".

Introduction

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Food Reward Friday

This week's luck winner... soy sauce!!

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Top Ten Health Topics

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