Tag Archives: Paleo diet

Which Diet Works Best For Weight Loss?

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  and I consider myself a keto-friendly cardiologist.

Recently I stumbled across a good review on the scientific evidence of various popular diets for weight loss. Obesity and its health consequences are clearly increasing and impacting the cardiovascular health of millions. As such, as a cardiologist it would be great to have a one true diet that is best for weight loss for my patients.

Unfortunately, as I discussed in my analysis of the DIETFITS study there isn’t a one size fits all dietary silver bullet. This recent review does a good job of analyzing the data and has some nice graphics.

Here’s the first graphic which summarizes the food groups allowed for 7 of the most popular diets

Is there any food group we can all agree on?

Yes, the non-starchy vegetables!

Dr. P’s Heart Nuts come in a close second (outlier Ornish recommends “moderation”. Extreme outlier Esselsytn who eschews all oils forbids nuts.)

Interestingly, the only one of these diets that bans red meat, chicken, seafood and eggs is the Ornish diet which is basically a vegetarian diet (see here for the lack of science behind this diet.)

Is there any food group that we all agree should be avoided? If we exclude the outlier Ornish  then there is unanimity that we should be avoiding added sugar and refined grains.

My recommended version of the Mediterranean diet says that high fat dairy is perfectly fine and actually preferred over processed skim or low fat dairy. Yogurt and cheese are encouraged.

Do Macronutrients Matter?

The second graphic nicely summarizes the macronutrient composition of these diets. The Atkins diet and ketogenic diets recommend less than 10% carbs whereas Ornish the outlier recommends less than 10% fat.

My recommended variation on the Mediterranean diet would lower the carb % to around 20% by avoiding starchy vegetables, most added sugar and most refined grains. I try to avoid ultra-processed foods completely. With this diet I am in some degree of ketosis (as measured by the fantastic Keyto device) most of the time although I’m not strictly following keto guidelines.

For example last night I had this delicious steak and smoked portabello quesadilla from Three Kings Pub. The tortilla alone contains about 40 grams of carbs, double the recommended amount for keto diets. I add elements of Three Kings Middle Eastern Sampler (Red pepper hummus, grilled eggplant relish, tzatziki, roasted head of garlic and dolmas. Served with grilled flatbread and an assortment of veggies) to get some of those universally acclaimed nonstarchy vegetables . I don’t utilize the balsamic reduction that is typically drizzled on the quesadilla because it tastes like pure sugar to me (sure enough it contains 11 grams of carbs)and I mostly avoid the grilled flatbread.

 Manipulation Of Diet Timing For Weight Loss

Breakfast is not the most important meal of the day and I only break my overnight fast when I get hungry which is typically around noon.

Variations on this type of intermittent fasting (periodic fasting or 5:2 diet, alternate-day fasting, time-restricted feeding, and religious fasting) have become popular. The review summarizes the science in this area as follows:

“There is growing evidence demonstrating the metabolic health benefits of IF. In rodents, these appear quite profound, whereas in humans they are sparse and need further investigation, especially in long-term studies. It has been suggested that IF does not produce superior weight loss in comparison with continuous calorie restriction plans [130], and there are limited data regarding other clinical outcomes such as diabetes, CVD, and cancer. IF diets seem safe and tolerable for adults…”

In other words, rats live longer with IF but we don’t know if humans do. If you find intermittent fasting helps you consume less calories through out the day and lose weight, go for it. For me fasting from 9 PM to late morning (typically 14-16 hours) give me greater energy and focus throughout the day and makes weight management simpler.

Conclusions: What Is The Best Diet For Weight Loss?

Both low carb and low fat fanatics will be disappointed in the conclusions of the review but I think it is reasonable:

There is no one most effective diet to promote weight loss. In the short term, high-protein, low-carbohydrate diets and intermittent fasting are suggested to promote greater weight loss and could be adopted as a jumpstart. However, owing to adverse effects, caution is required. In the long term, current evidence indicates that different diets promoted similar weight loss and adherence to diets will predict their success. Finally, it is fundamental to adopt a diet that creates a negative energy balance and focuses on good food quality to promote health.

I would

And here is the summary graphic

Dietetically Yours,

-ACP

N.B. With regard to the starchy vegetables, check out my “Potato Theory of Obesity.”

Source for images: Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting, and popular diets – ScienceDirect

And finally  (from  the  DietDoctor.com website) a graphic that illustrates the amount of healthy (nonstarchy!) vegetables that you would need to consume to reach 20 grams of carbs.

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!