Fat vs. Carbohydrate Overeating: Which Causes More Fat Gain?

Two human studies, published in 1995 and 2000, tested the effect of carbohydrate vs. fat overfeeding on body fat gain in humans.  What did they find, and why is it important?

We know that daily calorie intake has increased the US, in parallel with the dramatic increase in body fatness.  These excess calories appear to have come from fat, carbohydrate, and protein all at the same time (although carbohydrate increased the most).  Since the increase in calories, carbohydrate, fat, and protein all happened at the same time, how do we know that the obesity epidemic was due to increased calorie intake and not just increased carbohydrate or fat intake?  If our calorie intake had increased solely by the addition of carbohydrate or fat, would we be in the midst of an obesity epidemic?

The best way to answer this question is to examine the controlled studies that have compared carbohydrate and fat overfeeding in humans.

Horton et al.

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What Role Does Fat Play in A Healthy Diet?




I love it when other health-minded individuals contact me to share their work or research regarding a topic I have written about.  And, The Health-Minded reader, Julie Marsh, did just that!  I am very excited to share with you her piece on a subject that may be confusing for many: fats in our diet.  We get conflicting information on that topic. Which ones are okay to consume, which ones are not.  How do they each impact our health?

Julie is a free-lance writer but worked in health and nutrition after college but on becoming a mother decided to take a step back and follow her writing dream.  She now works freelance on a wide range of topics, but is always happiest tackling health and nutrition. And, I am glad she enjoys that topic as much as I do because she has some great information for you here today.  I wrote about the value of eating the Mediterranean Diet here and here and Julie's piece adds to the story.



Study Finds No Link between Saturated Fat Intake and Heart Disease Risk

If you currently limit your intake of butter, full fat dairy produce and meat, and carefully check food labels for the amount of saturated fat they contain, you’re not alone. For decades we have been told by health experts to cut back our intake of saturated fats to reduce our risk of cardiovascular problems and instead choose foods rich in unsaturated fats such as vegetable oils, nuts, seeds, avocados and oily fish. However, new research, published in the Annals of Internal Medicine, has cast some doubt on the benefit of limiting the amount of saturated fat in our diet.






Considering the evidence

The analysis, which looked at close to 80 quality studies, involving over half a million participants in total, found that people who ate most saturated fat were no more likely to develop heart disease than people who had the least amount of saturated fat in their diet. Equally, those people who ate a diet higher in unsaturated fat were just as prone to heart disease as those who consumed far less unsaturated fat. The research did, however, confirm that a higher intake of trans fats, found in certain soft margarines, fried foods and commercially baked goods like cakes, cookies, pastries, pizza, chips and frozen meals, increases your risk of coronary artery disease. While saturated fats may not be as unhealthy as previously thought, before you start adding steak, cheese and chocolate to your weekly shop, it’s important to consider the reasons for these findings. Saturated fats may offer some benefits, but this study doesn’t necessarily give you the go-ahead to up your intake of saturated fat, as your diet as a whole is also important.



Impact of saturated fat on cholesterol levels

Firstly, although saturated fats raise levels of LDL cholesterol, the type of cholesterol associated with narrowing of the arteries, it turns out that saturated fats increase a subset of larger LDL particles known as type-A, which are less likely to damage your arteries than small, dense type-B LDL particles. This is because the larger LDL molecules are less reactive, so less likely to trigger inflammation, which usually contributes to the formation of plaques on the coronary arteries. Certain saturated fats may even lower levels of LDL cholesterol, with the saturated fat stearic acid, which accounts for around half the saturated fatty acids in beef, rapidly converted into heart-healthy monounsaturated fat. The positive impact of heptadecanoic acid, a saturated fat found in dairy produce, may also explain why dairy consumption is not associated with heart disease risk.

Saturated fats additionally boost levels of protective HDL cholesterol, which removes cholesterol from the arteries, with a higher level of HDL associated with a reduced risk of coronary artery disease. This contrasts with trans fats, which raise harmful LDL cholesterol, while lowering beneficial HDL cholesterol. In view of the impact of trans fats on your cholesterol profile and the fact that many processed foods are high in both trans and saturated fat, consuming a diet high in saturated fat may indirectly increase your risk of future heart problems.




Low-fat, high carbohydrate diets are not beneficial

Another consideration is that no cardio-protective benefit was seen among those people who cut back on saturated fat because other aspects of their diet were not considered in these studies. People often swap high fat savory foods for extra bread and simply change from having chocolate, cookies and cakes to sweet foods that might be low in fat, but are just as high in sugar. This is relevant, as if saturated fats are replaced with extra carbohydrate in the diet, particularly sugary foods, this will not benefit cardiovascular health, as the amount of carbohydrate in your diet can also adversely affect your cholesterol profile.

For instance, high carbohydrate diets are linked to increased levels of damaging type-B LDL cholesterol and lower levels of HDL, as well as raised levels of triglycerides, which are another type of fat in the blood that increase your risk of heart disease. From this it seems that it is a carbohydrate rich diet that will do more damage to your arteries, so current advice from the American Heart Foundation is not to replace saturated fats with carbohydrates, but instead to replace them with monounsaturated and polyunsaturated fats. Indeed, research shows that both types of unsaturated fats lower LDL cholesterol, but monounsaturates, which are found in good quantities in olive and canola oil, avocados, nuts and seeds, have the advantage that they do not lower HDL cholesterol, unlike polyunsaturates, which are sourced from the likes of soyabean, corn and sunflower oil. While it is inadvisable to follow a low carbohydrate diet, including moderate portions of whole grains, such as oats, grainy bread and brown rice, which release their sugars more slowly will help to keep your lipid profile healthy.






Aim for a Mediterranean diet

The points above show why considering nutrients in isolation does not work particularly well when aiming to lower your risk of heart disease. Rather than aiming to eat less than a certain amount of saturated fat each day, you should consider the overall nutritional value of the foods you eat. This might be why a Mediterranean diet, which is rich in olive oil, fish and nuts, as well as including plenty of fruit, vegetables, pulses and whole grains, was shown to lower the risk of heart attacks and strokes more effectively than simply a low-fat diet.

The Mediterranean diet doesn’t exclude saturated fats, as after all cheese, yogurt, eggs and small amounts of meat are all included, but it is high in monounsaturates. It also offers fiber, antioxidants and other micronutrients beneficial to heart health in good supply and a Mediterranean approach to eating generally means a lower intake of refined carbohydrates than with low-fat diets. This recent study comparing a Mediterranean and low-fat diet in relation to cardiovascular disease was unfortunately not included in the analysis of different dietary fats on coronary heart disease risk. However, owing to the widely accepted benefits of the Mediterranean diet for cardio-protection, we should all aim to follow the Mediterranean food pyramid for better heart health.



Thanks so much, Julie! Please drop back in soon to teach us some more about how best to stay health-minded.

Note: This piece originally appeared here.

bread: photo credit: <a href="http://www.flickr.com/photos/19779889@N00/8385332010/">arbyreed</a> via <a href="http://photopin.com">photopin</a> <a href="http://creativecommons.org/licenses/by-nc-sa/2.0/">cc</a>
fish: photo credit: <a href="http://www.flickr.com/photos/paranoiasdelavida/4080181507/">Anikaviro</a> via <a href="http://photopin.com">photopin</a> <a href="http://creativecommons.org/licenses/by-nc/2.0/">cc</a>

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Garden Update: A Banner Year

Things are warming up here in Seattle and the flowers are blooming.  I just planted my first crops of the year-- potatoes and strawberries.

2013 was a banner year for my 500-square-foot urban vegetable garden, including my first experience growing and processing a grain.  I never got around to posting about it last year-- so here it is.

Interbay mulch technique

The bed on the right has been mulched with leaves, spent coffee
grounds, and burlap sacks ($1/sack at the local hardware store).
The beds on the left were planted with a rye-clover-vetch-pea
cover crop.  Paths are mulched with wood chips.
In the fall of 2012, I tried a new technique for improving the soil called "Interbay mulching".  This is a variation on sheet mulching, which involves placing uncomposted organic matter directly onto the garden soil in fall and letting it compost until the next growing season.  To Interbay mulch, you simply cover your sheet mulch with burlap.  This keeps everything moist, protects earthworms from bird predation so they can munch freely, and suppresses weeds.  I used leaves (carbon) and spent coffee grounds from a local coffee shop (nitrogen) for my organic matter.

When I pulled back the burlap last spring, I was initially disappointed.  The coffee grounds had disappeared completely, but there was still a lot of leaf matter left on the soil, indicating that it had only partially composted.  However, I later decided that it had worked well, because the soil structure underneath was improved and it seemed to be enriched with significant organic matter as well as a large population of fat earthworms.  The mulch suppressed weeds remarkably well, and the beds remained mostly clean for the rest of the season.

Those observations, combined with huge yields from the mulched beds, convinced me that it was worthwhile.

New tools
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More Graphs of Calorie Intake vs. BMI

In the last post, a reader commented that the correlation would be more convincing if I graphed calories vs. average BMI rather than the prevalence of obesity.  It was a valid point, so I went searching for average BMI values from NHANES surveys.  I dug up a CDC document that contains data from surveys between 1960 and 2002 (1).  Because these data only cover five survey periods, we only get five data points to analyze, as opposed to the eight used in the last post.  The document contains BMI values for men and women separately, so I averaged the two to approximate average BMI in the general adult population.  It's also worth noting that I use the approximate midpoint of the survey period as the year.

First, a graph of average BMI over time.  It went up:



Now, let's see how well average BMI correlates with calorie intake:


The correlation between calorie intake and obesity prevalence was remarkable, but this correlation is simply incredible.  An R-squared value of 0.98 indicates that daily calorie intake and average BMI are almost perfectly correlated.

We can further deduce that each 100-calorie increase in daily food intake is associated with an 0.62-point increase in average BMI among US adults.  

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Calorie Intake and the US Obesity Epidemic

Between 1960 and 2008, the prevalence of obesity in US adults increased from 13 to 34 percent, and the prevalence of extreme obesity increased from 0.9 to 6 percent (NHANES surveys).  This major shift in population fatness is called the "obesity epidemic".


What caused the obesity epidemic?  As I've noted in my writing and talks, the obesity epidemic was paralleled by an increase in daily calorie intake that was sufficiently large to fully account for it.  There are two main sources of data for US calorie intake.  The first is NHANES surveys conducted by the Centers for Disease Control.  They periodically collect data on food intake using questionnaires, and these surveys confirm that calorie intake has increased.  The problem with the NHANES food intake data is that they're self-reported and therefore subject to major reporting errors.  However, NHANES surveys provide the best quality (objectively measured) data on obesity prevalence since 1960, which we'll be using in this post.

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Uncovering the True Health Costs of Excess Weight

Is excess weight hazardous to health, or can it actually be protective?  This question has provoked intense debate in the academic community, in some cases even leading researchers to angrily denounce the work of others (1).  There is good evidence to suggest that excess body fat increases the risk of specific diseases, including many of our major killers: diabetes, heart attack, stroke, heart failure, cancer, and kidney failure (2).  Yet strangely, the studies relating excess weight to the total risk of dying-- an overall measure of health that's hard to argue with-- are inconsistent.  Why?
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New Position with Nestlé

Warning -- Satire -- April Fool's Post

I'm happy to announce that I've accepted a Product Research and Development position with NestlĂ© Foods.  NestlĂ© is known for its skillful application of 'neuromarketing'-- using neuroscience to enhance product development and sales-- and the company recruited me for my background in neuroscience and food reward.

As Whole Health Source readers know well, food reward has a major impact on food selection and consumption, and therefore it has huge potential as a product development strategy.  Although product development by the food industry has always relied to some extent on a basic understanding of food reward, corporations still lag far behind the cutting edge of food reward research, and they are therefore missing out on a major opportunity to drive repeat purchase and consumption behavior and increase total sale volume.  I plan to leverage science-corporate synergy to develop food product solutions that people LOVE*.

Even more exciting, NestlĂ© has asked me to lead a strategic partnership initiative with Coca-Cola to utilize neuromarketing to tailor beverage product development specifically for children, who have a somewhat different set of reward criteria than adults.  We're excited to develop product solutions that kids LOVE* even more than current offerings, by scientifically designing new combinations of flavors, sweeteners, and totally safe habit-forming drugs such as caffeine.

Both companies have been very responsive to my nutritional concerns about processed foods, and so we're working together to make healthier products.  Here are some of the changes we're discussing:
  • Adding vitamin C and cod liver oil to chocolate.
  • Replacing a portion (1.7%) of the sugar in beverages with stevia across the board.
  • Stealthily decreasing the portion size of beverages.  To do this, we'll increase the thickness of the plastic bottles so the exterior of the bottle is the same size, but the actual beverage content is reduced by 0.2 oz.
  • Getting these healthy snacks and beverages back into schools where kids can enjoy them!
One of the first things we discussed is getting the advertising department at NestlĂ© to write guest posts for Whole Health Source.  This will be a fun way for WHS readers to stay informed of current NestlĂ© products and what we have coming down the pipeline!

April Fools!!!!!!


* Learned Obedience Via Eating

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