Tag Archives: Weight Loss

Low-Fat Versus Low-Carb Diet: DIETFITS Show Both Can Work If They Are “Healthy”

In the ongoing nutritional war between adherents of low-fat and low-carb diets, the skeptical cardiologist has generally weighed in on the side of lower carbs for weight loss and cardiovascular health.

I’ve questioned the vilification of saturated fat and emphasized the dangers of added sugar. I’ve even dabbled in nutritional ketosis.

The science in  nutrition is gradually advancing and the DIETFITS study recently published in JAMA is a welcome addition.

DIETFITS is a  really well done study which provides important insights into three huge questions about optimal diet:

  1. Should we choose a low-fat or a  low-carb diet for  weight loss and cardiovascular health?
  2. Do baseline insulin dynamics predict who will respond to low-fat versus low-carb diet?
  3. Can we predict who will respond to low-fat versus low-carb by genetic testing?

The Details Of DIETFITS

Stanford investigators recruited 609 San Francisco area individuals between the ages of 18 to 50 years with BMI of 28 to 40  and randomized them to a “healthy” low-fat diet or a “healthy” low-carb diet.

During the first 8 weeks of the study, low-fat participants were instructed to reduce fat consumption to <20 gm/ day while the low carb participants were instructed to reduce digestible carbohydrate to <20 gms/day.

Then individuals were allowed to add back fats or carbs back to their diets in increments of 5 to 15 g/d per week until “they reached the lowest level of intake they believed could be maintained indefinitely.”  Importantly no explicit instructions for energy restriction were given.

The “healthy” instructions for both groups were as follows

  1. maximize vegetable intake
  2. minimize intake of added sugar, refined flours and trans-fats
  3. focus on whole foods that are minimally processed, nutrient dense and prepared at home whenever possible

Dietfits Outcomes-Diet And Weight

Major findings

  1. Total energy intake was reduced by 500-600 kcal/d for both groups
  2. The low-fat vs the low-carb intake at 12 months was 48% versus 30% for carbs, 29 vs 43% for fat and 21 vs 23% for protein.
  3. Mean 12 months weight change was -5.3 kg for low-fat vs 6-6.0 kg for low-carb which was not significantly different
  4. There was no difference between groups in body fat percentage or waist circumference
  5. Both diets improved lipid profiles and lowered blood pressure, insulin and glucose levels
  6. LDL (bad cholesterol) declined more in the low-fat group whereas HDL (good cholesterol) increased more and triglycerides declined more in the low-carb group.

Thus both diets were successful for weight loss and both improved risk markers for cardiovascular disease after a year.

DIETFITS- Can Genes and Insulin resistance Predict Best Diet?

Surprisingly, the study found no significant diet-genotype interaction and no diet-insulin secretion interaction with weight loss.

This means that they could not predict (as many believed based on earlier studies) who will benefit from a low carb diet based on either currently available genetic testing or a generally accepted measure of insulin resistance.

As the authors point out, these findings “highlight the importance of conducting large, appropriately powered trials such as DIETFITS for validating early exploratory analyses.”

DIETFITS-Perspectives

As you can imagine this study has led to quite an uproar and backlash from dedicated combatants in the macronutrient wars.

A reasoned summary and response from Andreas Eenfeldt, a low carb proponent can be found on his excellent low carb/keto Diet Doctor site here.

Eenfeldt concludes

If I’m allowed to speculate, the reason that we did not see any major additional benefit from low carb in this study is that the groups ended up so similar when it came to bad carbs. The low-fat group ended up eating fewer carbs too (!) and significantly less sugar, while the low-carb group ended with a somewhat weak low-carb diet, reporting 130 grams of carbs per day.

Eenfeldt emphasizes that low-fat diets never “win” these macronutrient dietary skirmishes:

On the whole, this study adds to the 57 earlier studies (RCTs) comparing low carb and low fat for weight loss.

From a standing of 29 wins for low carb, zero for low fat and 28 draws, we now have 29 wins for low carb and 29 draws. The wins for low fat stay at zero.

Larry Husten at Cardiobrief.org in his analysis of the study quotes a number of experts including Gary Taubes, the low carb pioneering journalist

Taubes speculates “that the weight loss may have been similar not because any diet works if you stick with it and cut calories (one possible interpretation) but because of what these diets had in common — avoid sugar, refined grains, processed foods. Whether the low-carb arm would have done even better had Gardner kept their carbohydrates low is something this study can’t say. (And Ornish [low-fat diet proponent] would probably say the same thing about fat consumption.)”

The low-fat or vegan disciples seem to have had a muted response to this study. I can’t find anything from John McDougal , Dean Ornish, Caldwell Esselstyn or Joel Fuhrman.

Readers feel free to leave comments which  link to relevant analysis from the low-fat proponents.

Dietfits-Perspective Of The Participants

Julia Volluz at Vox wrote a fascinating piece recently which involved interviewing some of the participants in this study.

She points out that although the average DIETFITS participant lost over 10 pounds, “Some people lost more than 60 pounds, and others gained more than 20 during the year.”

LOW_FAT_LOW_CARBS_DIETS1__1_

She obtained permission from the lead author, Christopher Gardner  and interviewed  “Dawn, Denis, Elizabeth*, and Todd — two low-fat dieters and two low-carb dieters — about their experiences of succeeding or faltering in trying to slim down”

LOW_FAT_LOW_CARBS_DIETS1

I highly recommend reading the entire article for details but Volluz concludes

And that leads us to one of the burning mysteries of diets: how to explain why some people fail where others succeed — or the extreme variation in responses. Right now, science doesn’t have compelling answers, but the unifying theme from the four study participants should be instructive: The particulars of their diets — how many carbs or how much fat they were eating — were almost afterthoughts. Instead, it was their jobs, life circumstances, and where they lived that nudged them toward better health or crashing.

DIETFITS-Importance of “Healthy” Diet

Most likely the success of both of these diets is due to the instruction that both groups received on following a “healthy” diet. This guidance is remarkably similar to what I advocate and is something that combatants in the diet wars ranging from paleo to vegan can agree on.

The JAMA paper only provides the description I listed above but Volluz adds that participants were instructed to:

… focus on whole, real foods that were mostly prepared at home when possible, and specifically included as many vegetables as possible, every day … choose lean grass-fed and pasture-raised animal foods as well as sustainable fish ... eliminate, as much as possible, processed food products, including those with added sugars, refined white flour products, or trans-fats … prepare as much of their own food as possible. …

Indeed, if you want to see a very detailed description of the instructional process for participants check out the very detailed description of the methods here.

Yours in Health,

-ACP

N.B. I was searching for a reasoned response to this study from the low fat camp and to my surprise came across this fascinating video featuring the lead author of the study, Christopher Gardner, on (no fat/vegan) John McDougal’s YouTube site. Gardner is clearly on the side of sustainable, local , ethical food consumption but to his credit, his research , publications and comments on DIETFITS don’t reveal this.

Pistachios: Are Their Shells A Portal to Contamination, The Key To Weight Loss, or A Manicure Destruction Device?

The results of the “Fourth Nut” poll are in and the winner is a nut first cultivated in Bronze Age Central Asia,

Almost 60% of readers who took the time to vote selected the pistachio nut.

Coming in a distant second was the macadamia nut. One reader prized it because it only contained saturated fat and monounsaturated fats. Another bemoaned their candy-like quality which makes over-consumption an issue.

A couple of readers were strong proponents of Brazil nuts. This prompted me to enter a selenium rabbit hole from which I have yet to emerge. If I can escape with my selenoproteins intact I’ll let you know.

Pistachios are a fine choice from a health standpoint and seem to be embraced by all nutritional cults, with the exception of  the very nutty Caldwell “NO OIL” Esselstyn’s acolytes.

The Pistachio Principle PR Institute

I’m in the process of sorting through the nutritional studies on pistachios, and the hardest part is determining which data are sponsored by the pistachio industry.

For example, poorly researched online articles about pistachios will typically state that “research suggests” that “pistachios could help to reduce hypertension and promote development of beneficial gut microbes. They’re even gaining credibility as a tool for weight loss”

The first reference is an open access review article which clearly just wants to extoll any and all positive pistachio data and was paid for by the American Pistachio Growers. The second article comes directly from “The Pistachio Health Institute,” a PR voice for the pistachio industry.

To Shell or Not to Shell

My major dilemma was deciding if the pistachios should be shelled or left in-shell. (This has led me down the pistachio production rabbit hole).

I was concerned that the outsides of the pistachio shells could be contaminated in some way and the idea of mixing them in with unshelled nuts seemed a little strange.

If you Google images of mixed nuts pistachio you only see mixtures with unshelled pistachios.

Why, then, are most pistachios sold and consumed in-shell?

According to How Stuff Works Louise Ferguson, author of the Pistachio Production Manual believes:

Between 70 and 90 percent of pistachios develop a natural split in their shells during the growing process, After those pistachios are shaken off the trees by harvesting machines, they can be salted and roasted while still inside the shells as that natural crack allows heat and salt access to the nut, eliminating a step in the industrial process and saving processors some money.

The pistachio PR machine would also have us believe that eating pistachios in-shell can lead to weight loss:

Why choose any other nut?

This pistachios principle is based on 2 studies in the journal Appetite (seems to be a legitimate journal) by JE Painter of the department of “Family and Consumer Sciences” Eastern Illinois University in Charleston, Illinois.

I’m awaiting a full copy of the paper, but the abstract notes that students offered in-shell pistachios consumed only 125 calories, whereas those offered shelled pistachios consumed 211 calories yet “fullness and satisfaction” were similar.

My skeptical sensors were exploding when I read about this study. I doubt that it will ever be reproduced.

If we look at cost, an unofficial analysis revealed:

The pre-shelled pistachios were priced at $5.99 for 6.3 oz of nuts.

The 8 oz bag of pistachios were priced at $4.49.  After shelling he was left with 4.3 oz of nuts.

Un-shelled pistachios = $1.04 per oz.

Shelled pistachios = $0.95 per oz.

If you go the lazy route, you save $.09 per oz!

Most likely, the fourth nut will be a shelled pistachio unless readers convince me otherwise or the blather from the pistachio PR machine  annoys me too much.

The eternal fiance’e has just weighed in and tells me that women who care about their well-groomed  nails will not consume  in-shell pistachio nuts for fear of damaging their manicures.

That, my friends, is the  nail in the coffin for shelled pistachios as the fourth nut.

Pistachoprincipaly Yours,

-ACP

Which Popular Diets Are Supported By Science?

Which of the currently popular and highly marketed diets are best for weight loss and cardiovascular health? Can science answer this question?
questI just took a 90 minute online “course” taught by Eric Rimm of the Harvard School of Public Health; I think he does a good job of summarizing the scientific evidence on this topic and presenting it in a way that the average layperson can understand.

You can sign up for free here. If you’re not interested in spending your time watching him, here are my take-home points:

1. When evaluating the efficacy of a diet to control weight, the best evidence comes from observational studies that involve tens of thousands patients over decades and/or (preferably) randomized control trials that last at least two years.

2. The Paleo, Wheat-belly, gluten-free, Atkins, South Beach, and Zone diets do not have good evidence supporting sustained weight loss or health benefits. In general, people who follow these diets will be consuming lots of fresh vegetables, nuts and “healthy” fats and avoiding processed food, which is good, and this likely explains any  benefits achieved.

3. Of all the diets, the low-fat diet (Ornish/Pritikin/China Study are the extreme examples of this) is the only one which has strong evidence showing an absence of benefit.

Yes, the diet that was recommended to Americans for 30 years does not help with weight loss in the long run for the vast majority of individuals.

As Rimm says “We need to eliminate the dogma that low fat is needed for weight loss.”

Dr. Rimm spends a good amount of time on this, highlighting findings from a study of 50 thousand women (the Women’s Health Initiative), which lasted for 9 years. In the first year, women on the low-fat diet (counseled to consume <20% of calories in the form of fat), lost more weight than those on the usual diet, however, in subsequent years they gained back the weight and did not differ from the higher fat consuming group.

There was also no difference in the rates of dying or contracting any disease between the two groups.

The problem with the low fat diet was adherence. Although a very small percentage of individuals can remain on a  vegan or really low-fat diet and successfully lose weight and be healthy, the majority of us can’t.

By the end of the study the low fat group had increased their fat consumption to 28% which was not much less than what the usual group was consuming (32%)

Over time, the low fat group gradually added fats because they taste better and they are more satiating.

4. The DASH diet has evidence showing improvement in blood pressure, and cholesterol. The heart of the DASH diet is an eating plan rich in fruits and vegetables, low-fat and nonfat dairy, along with nuts, beans, and seeds.

Unfortunately, it was developed in an era when all fats were considered bad and proof of cardiovascular benefit is lacking.

5. Mediterranean diet. Gets a strong pass from Rimm with multiple studies showing benefits in both weight reduction and reduction of cardiovascular mortality.

The Med diet also demonstrates good long term adherence because of its diversity and inclusion of fat (for taste and satiety).

Improved adherence has been shown to be the major determinant of diet success. When you add regular counseling and support to any diet it works better and can be sustained.

This is the Mediterranean diet I recommend:

1. Lots of fresh fruits and vegetables. These contain fiber, phytochemicals, minerals.

2. Two servings of fish per week.

3. Plenty of nuts (and drupes!), legumes, and seeds.

4. Grains are allowed, preferably all whole grains.

5. Moderate alcohol consumption (1 drink/day for women, 2 drinks/day for men).

6. Olive oil.

7. Meat is allowed.

8. Eggs and dairy are allowed.

Dr. Rimm is still clinging to the idea that all saturated fats should be limited and preferfat replacementably replaced by PUFAs or MUFAs. He presented this graphic (courtesy of Dr. Willet at Harvard), which illustrates the most prevalent concepts about saturated fat replacement.

Risk of heart disease is on the y axis. According to this graph, If you replace saturated fat with trans fat or sugar/refined starch, risk goes up.

If you replaced saturated fat with unsaturated vegetable fats or whole grains, risks go down.

Most nutritional experts now can agree on the importance of the key components of the Med diet and the lack of efficacy of low fat diets.

The disagreement comes in whether moving that arrow down from saturated fat to unsaturated fat is truly beneficial for weight management or cardiovascular health.

Good Fats and Bad Fats?

My own take on the good fat/bad fat controversy is as follows:

There are multiple types of saturated fats and multiple types of unsaturated fats and the scientific evidence is not currently robust enough to make the claim that replacing any saturated fat  with any unsaturated fat is a healthy change.

There is no evidence that low-fat or no fat dairy is healthier than full fat dairy (see here and here). Eating no, or low, fat yogurt with the natural fat replaced by sugar and other additives likely moves the arrow up, raising your risk. This kind of processed food gets a pass from mainstream nutritionists for some reason.

Saturated fat from pasture-raised pigs and cows consumed in moderation is not unhealthy or weight gain promoting.

In the end, Dr. Rimm and I agree on about 95% of the science and recommendations in his course.

Take a look and you can tell your friends that you just passed a Harvard course with flying colors!

 

 

 

Scintillating Findings From New Orleans: Low Carb Diet Is Better than Low Fat for Losing Weight and Preventing Heart Disease

The SC and the Significant Other of the SC at Commander's Palace following an investigation of shrimp and grits.
The SC and the Significant Other of the SC at Commander’s Palace following an investigation of shrimp and grits.

The Skeptical Cardiologist is in New Orleans this weekend on a dedicated quest to research low carb diets.

The low fat diets recommended by government guidelines and national organizations like the American Heart Association don’t help most individuals lose weight and they don’t lower  the risk of heart disease. It’s very hard to understand why these are still promulgated by these organizations.

Some diets, such as the Atkins, South Beach and Paleo diets, advocate very low carbohydrate consumption and have helped many successfully lose weight.  However, due to the high fat in such diets, there has been concern about their overall effect on  cholesterol levels and heart disease.

A new study published in the Annals of Internal Medicine addressed the question of which of these dietary  approaches is best. Researchers at Tulane University (located inNew Orleans!)  randomly divided   148 obese (BMI>30) men and women (88% were women and 51% were black) into two  groups: a low-carbohydrate group that was encouraged to consume no more than 40 grams of carbohydrates  per day (the amount of two slices of  bread), and a low-fat group, which was encouraged to consume less than 30 percent of their calories from fat and 55 percent from carbohydrates (based on the National Education Cholesterol Program guidelines).

Interestingly neither group was instructed to lower their overall calorie consumption and both groups were instructed NOT to change their overall physical activity level (the researchers were trying to minimize factors effecting their results other than the percentage of fat/carbs).

The funding source for the study was the National Institutes of Health so we can consider the study unbiased by industry.

After 12 months, the low-fat group had lost 1.8 kg (2.2lbs=1kg) and the low-carb group had lost 5.3 kg.

The low-carb group had lost 8 pounds more, a difference that was highly  statistically significant (p<.001).

In addition, in the low-carb group fat mass had declined by 1.2% whereas it had risen by 0.3% in the low-fat group.

In other words, the low-carb group was losing body fat but the low-fat group was just losing lean body mass.

My patients, like most Americans, have had the lie that fat consumption causes obesity and contributes to fatty plaques in their arteries drummed into their heads for decades and fear low-carb diets because of concerns that they will cause their cholesterol levels to rise and increase their risk of heart disease.

This new study, however, showed that the low-carb diet (with almost double the amount of saturated fat consumed compared to low-fat diet) actually improved the subjects’ heart risk profile.

Low Carb Diet Improves Cardiac Risk Profile

At 12 months, there was no difference in the total or LDL (bad cholesterol) levels between the two groups. However, the good (HDL) cholesterol had significantly increased in the low-carb group causing a decrease in the ration of total to HDL cholesterol. The low-fat group had no increase in HDL. Triglycerides dropped in both groups but significantly more in the low-carb group.

Atherosclerosis is not just related to the cholesterol profile as I have discussed here,  but it is a complex process involving multiple factors, including inflammation.  A simple blood test, the C-reactive protein or CRP tracks inflammation. The CRP dropped by 6.7 nmol/L in the low-carb group and rose by 8.6 nm/L in the low-fat group. Lower CRP levels have been associated with lower risk of cardiovascular events in multiple studies.

This was a small study (but actually one of the largest prospective dietary studies available) but really well done.

The major take home points are as follows:

  1. Low-carb diets for many are a very effective weight loss approach
  2. Low-carb diets, even with their higher saturated and overall  do not adversely effect the cholesterol profile or increase risk of heart disease.
  3. This study suggests that low-carb diets improve good cholesterol, lower inflammation and are likely, therefore, long term to reduce the risk of heart attacks and strokes.

Realistic Dietary Approaches

I have found the extremely low-carb diets such as Atkins to be very hard for my patients to follow long term.  Some modification of  the strict limits on carb consumption are necessary I think to make diets interesting and healthy.

Although the goal of this study was to have the low-carb group consume less than 40 grams, the average carb consumption was 93 grams at 6 months and 127 grams at 12 months, a much more sustainable level of carb intake.

The first and most important thing anyone can do if they  want to lose weight and improve their cardiovascular risk profile is eliminate added sugar from their diet.

Sugar-sweetened beverages are an easy first step. But equally important is avoiding foods masquerading as healthy due to their low fat content. Low-fat yogurt and smoothies, for example, are loaded with empty sugar calories. You are much better off consuming the full fat varieties as I have pointed out here.

This is the Skeptical Cardiologist signing off from beautiful New Orleans where my next investigation will be on the cardiovascular consequences of crawfish étouffée plus dixieland jazz.