Do Diets Work?

Written by Dr. Steve Chaney on . Posted in current health articles, Food and Health, Obesity

dietingObesity in America?

Author: Dr. Stephen Chaney

If you are like most Americans, you are either overweight yourself or have close friends and family who are overweight. That’s because 69% of Americans are currently overweight, and 36% of us are obese. Worldwide the latest estimates are that 1.5 billion adults are overweight or obese.

A new report, How The World Could Better Fight Obesity,  estimates that obesity is a $2 trillion drain on the world’s economy. That is equivalent to the global cost of war & terrorism and of smoking – and is double the global costs of alcoholism and global warming!

If you are like most Americans you have tried a number of diets over the years. All of them promised that they had the “secret” to permanent weight loss. You lost some weight initially, but here you are a few years later weighing as much as ever.

You are probably beginning to wonder whether any diets work long term. According to the latest study, the answer may just be “no”.

Really, Do Diets Work?

This study (Atallah et al, Circulation Cardiovascular Quality and Outcomes, 7: 815-827, 2014) was a systemmatic review of all of the randomized controlled studies of the four most popular diet plans – Weight Watchers, Akins, Zone and South Beach.

In case, you are unfamiliar with these diets, here is their philosophy:

  • Weight watchers is a food, physical activity and behavior modification plan that utilizes a point system to control calorie intake and features weekly group sessions.
  •  Atkins is based on very low carbohydrate intake, with unlimited fat and protein consumption.
  •  South Beach is relatively low carbohydrate, high protein diet that focuses on low-glycemic index carbohydrates, lean proteins, and mono- and polyunsaturated fats.
  • Zone is a low carbohydrate diet that focuses on low-glycemic load carbohydrates, low-fat proteins and small amounts of good fats.

The investigators restricted their analysis to studies that were greater than 4 weeks in duration and either compared the diets to “usual care” or to each other. (The term usual care was not defined, but most likely refers to a physician giving the advice to eat less and exercise more).

Twenty six studies met their inclusion criteria. Fourteen of those studies were short-term (< 12 months) and 12 were long-term (>12 months). Of the long-term studies, 10 compared individual diet plans to usual care and 2 were head-to-head comparisons between the diet plans (1 of Atkins vs Weight Watchers vs Zone and 1 of Weight Watchers vs Zone vs control). The majority of participants in these studies were young, white, obese women. Their average age was 45 years and their average weight at the beginning of the studies was 200 pounds.

What Did This Study Show?

If you have struggled with your weight in the past, you probably won’t be surprised by the result of the study.

  •  Short-term weight loss was similar for Atkins, Weight Watchers and Zone in the two head-to-head studies.
  •  At 12 months, the 10 studies comparing individual diets to usual care (physician’s advice to eat less and exercise more) showed that only Weight Watchers was slightly more effective than usual care (physician’s advice to lose weight). The average weight loss at 12 months was 10 pounds for Weight Watchers and 7 pounds for usual care. That is a 3 pound difference for all of the additional effort and expense of Weight Watchers!
  • When they looked at the two head-to-head studies at 12 months, there was no significant differences between the diets. Average weight loss in these studies was 7 pounds for Weight Watchers, 7 pounds for Atkins, 5 pounds for Zone and 5 pounds for usual care. There was only one study comparing the South Beach diets with usual care. It was a study comparing the results with severely obese patients following gastric bypass surgery, and it also found no difference between the diet program and usual care. Based on hype about these diets, you were probably expecting more than a 5 to 7 pound weight loss 12 months later!
  •  By 24 months 30-40% of the weight had been regained for the Atkins and Weight Watchers diets, which was comparable to the results for patients who were just told to eat less and exercise more. Not only was the weight loss modest, it also did not appear to be permanent.
  •  Finally, many of the studies included in this review also looked at improvement in other health parameters such as HDL cholesterol levels, LDL cholesterol levels, triglycerides, blood pressure and blood sugar control. The Atkins diet gave slightly better results with HDL levels, triglyceride levels and blood pressure in the short-term studies, but there was no significant differences for any of these parameters in the long-term head-to-head studies. None of the diets were any healthier than the others.

The investigators concluded: “Our results suggest that all 4 diets are modestly efficacious for short-term weight loss, but that these benefits are not sustained long-term.

A similar study in 2005 compared the Weight Watchers, Jenny Craig and LA Weight Loss diets (Tsai et al, Annals of Internal Medicine, 142: 56-66, 2005) and concluded “…the evidence to support the use of major commercial and self-help weight loss programs is suboptimal”.

weight loss and obesityA Weight Loss Diet That Actually Works?

My personal recommendation for the initial weight loss is a high protein diet – one that provides about 30% of calories from healthy protein and moderate amounts of healthy carbohydrates and healthy fats. The protein should be high enough quality so that it provides 10-12 gram of the essential amino acid leucine because leucine specifically stimulates muscle growth. The combination of high protein and leucine preserves muscle mass while you are losing weight. That is important because it keeps your metabolic rate high without dangerous herbs or stimulants.

However, the high protein, high leucine diet is still just a diet. It is an excellent choice for the initial weight loss, but what about long-term weight control?

The authors of this study said: “Comprehensive lifestyle interventions aimed at curbing both adult and childhood obesity are urgently needed. Interventions that include dietary, behavioral and exercise components…may be better suited to [solve] the obesity epidemic.” I agree.

The Bottom Line:

Your suspicions are correct. Diets don’t work!

A recent systematic review of 26 randomized controlled clinical trials of the Weight Watchers, Atkins, Zone & South Beach diets compared to the usual standard of care (recommendations to eat less and exercise more) concluded:

1) Contrary to what the advertisements promise, after 12 months all four diets gave comparable and very modest (5-7 pounds) total weight loss. The results with the diets were not significantly different than for patients who were simply told to eat less and exercise more.

2) By 24 months 30-40% of the weight had already been regained.

3) A previous systematic review of the Weight Watchers, Jenny Craig, and LA Weight Loss diet programs came to a similar conclusion.

4) My personal recommendation for the initial weight loss is a diet that is high in protein and the amino acid leucine because that type of diet preserves muscle mass.

5) For permanent weight control the authors of the recent systematic review recommended comprehensive lifestyle interventions that include permanent changes in diet, behavior and exercise. I agree. Diets never work long term – lifestyle change does!

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Comments (1)

  • Merlena Cushing

    |

    Thanks for this excellent article. You are truly a help to me in explaining these differences. Glad you had hyperlinks to your two previous articles, too. I have requested Corporate make further critique of the HFLC diets so I can refute those with precise rebuttal – piece by piece. They have been working on my request according to field services. It has been a week now. Hope to hear soon. Nedra told me when I asked (Nutrition Matters seminar) that to answer it in depth, she would need more time – a whole seminar session – approximately 1 1/2 hours.. She had recently been to a huge seminar on the “keto” diets.

    I’m adding this article to the many by you which address most of what I have needed.

    By the way, the hyperlink to your comments is not live (gives an error message) in case you wonder why you haven’t had any until now. I had to take a circuitous route to get to an article that said “LEAVE A COMMENT” at the bottom.

    Thanks again for all of the good you do! Blessings, Merlena

    Reply

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Latest Article

Can Plant-based Diets Be Unhealthy?

Posted September 10, 2019 by Dr. Steve Chaney

Do Plant-Based Diets Reduce Heart Disease Deaths?

Author: Dr. Stephen Chaney

 

plant-based diets vegetablesPlant-based diets have become the “Golden Boys” of the diet world. They are the diets most often recommended by knowledgeable health and nutrition professionals. I’m not talking about all the “Dr. Strangeloves” who pitch weird diets in books and the internet. I am talking legitimate experts who have spent their life studying the impact of nutrition on our health.

Certainly, there is an overwhelming body of evidence supporting the claim that plant-based diets are healthy. Going on a plant-based diet can help you lower blood pressure, inflammation, cholesterol and triglycerides. People who consume a plant-based diet for a lifetime weigh less and have decreased risk of heart disease, diabetes, and cancer.

But, can a plant-based diet be unhealthy? Some people consider a plant-based diet to simply be the absence of meat and other animal foods. Is just replacing animal foods with plant-based foods enough to make a diet healthy?

Maybe not. After all, sugar and white flour are plant-based food ingredients. Fake meats of all kinds abound in our grocery stores. Some are very wholesome, but others are little more than vegetarian junk food. If you replace animal foods with plant-based sweets, desserts, and junk food, is your diet really healthier?

While the answer to that question seems obvious, very few studies have asked that question. Most studies on the benefits of plant-based diets have compared population groups that eat a strictly plant-based diet (Seventh-Day Adventists, vegans, or vegetarians) with the general public. They have not looked at variations in plant food consumption within the general public. Nor have they compared people who consume healthy and unhealthy plant foods.

This study (H Kim et al, Journal of the American Heart Association, 8:e012865, 2019) was designed to fill that void.

 

How Was The Study Done?

plant-based diets studyThis study used data collected from 12,168 middle aged adults in the ARIC (Atherosclerosis Risk in Communities) study between 1987 and 2016.

The participant’s usual intake of foods and beverages was assessed by trained interviewers using a food frequency questionnaire at the time of entry into the study and again 6 years later.

Participants were asked to indicate the frequency with which they consumed 66 foods and beverages of a defined serving size in the previous year. Visual guides were provided to help participants estimate portion sizes.

The participant’s adherence to a plant-based diet was assessed using four different well-established plant-based diet scores. For the sake of simplicity, I will include 3 of them in this review.

  • The PDI (Plant-Based Diet Index) categorizes foods as either plant foods or animal foods. A high PDI score means that the participant’s diet contains more plant foods than animal foods. A low PDI score means the participant’s diet contains more animal foods than plant foods.
  • The hPDI (healthy plant-based diet index) is based on the PDI but emphasizes “healthy” plant foods. A high hPDI score means that the participant’s diet is high in healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) and low in animal foods.
  • The uPDI (unhealthy plant-based diet index) is based on the PDI but emphasizes “unhealthy” plant foods. A high uPDI score means that the participant’s diet is high in unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) and low in animal foods.

For statistical analysis the scores from the various plant-based diet indices were divided into 5 equal groups. In each case, the group with the highest score consumed the most plant foods and least animal foods. The group with the lowest score consumed the least plant foods and the most animal foods.

The health outcomes measured in this study were heart disease events, heart disease deaths, and all-cause deaths. Again, for the sake of simplicity, I will only include 2 of these outcomes (heart disease deaths and all-cause deaths) in this review. The data on deaths were obtained from state death records and the National Death Index. (Yes, your personal information is available on the web even after you die.)

 

Do Plant-Based Diets Reduce Heart Disease Deaths?

plant-based diets reduce heart deathsThe participants in this study were followed for an average of 25 years.

The investigators looked at heart disease deaths over the 25 years and compared people with the highest intake of plant foods to people with the highest intake of red meat and other animal foods. The results were:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods (whole grains, fruits, vegetables, nuts, legumes, coffee and tea) had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods (refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts) had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

What Else Did The Study Show?

The investigators made a couple of other interesting observations:

  • The association of the overall diet with heart disease and all-cause deaths was stronger than the association of individual food components. This underscores the importance of looking at the effect of the whole diet on health outcomes rather than the “magic” foods you hear about on Dr. Strangelove’s Health Blog.
  • Diets with the highest amount of healthy plant foods were associated with higher intake of carbohydrates, plant protein, fiber, and micronutrients, including potassium, magnesium, iron, vitamin A, vitamin C, folate, and lower intake of saturated fat and cholesterol.
  • Diets with the highest amount of unhealthy plant foods were associated with higher intake of calories and carbohydrates and lower intake of fiber and micronutrients.

The last two observations may help explain some of the health benefits of plant-based diets.

 

Can Plant-Based Diets Be Unhealthy?

plant-based diets unhealthy cookiesNow, let’s return to the question I asked at the beginning of this article: “Can plant-based diets be unhealthy?” Although some previous studies have suggested that unhealthy plant-based diets might increase the risk of heart disease, this study did not show that.

What this study did show was that an unhealthy plant-based diet was no better for you than a diet containing lots of red meat and other animal foods.

If this were the only conclusion from this study, it might be considered a neutral result. However, this result clearly contrasts with the data from this study and many others showing that both plant-based diets in general and healthy plant-based diets reduce the risk of heart disease deaths and all-cause deaths compared to animal-based diets.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

There is one other subtle message from this study. This study did not compare vegans with the general public. Everyone in the study was the general public. Nobody in the study was consuming a 100% plant-based diet.

For example:

  • The group with the highest intake of plant foods consumed 9 servings per day of plant foods and 3.6 servings per day of animal foods.
  • The group with the lowest intake of plant foods consumed 5.4 servings per day of plant foods and 5.6 servings per day of animal foods.

In other words, you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet.

 

The Bottom Line

A recent study analyzed the effect of consuming plant foods on heart disease deaths and all-cause deaths over a 25-year period.

When the investigators looked at heart disease deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had a 19-32% lower risk of dying from heart disease than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

When the investigators looked at all-cause deaths over the 25 years:

  • People with the highest intake of plant foods and the highest intake of healthy plant foods had an 11-25% lower risk of dying from any cause than people with the highest intake of red meat and other animal foods.
  • People with the highest intake of unhealthy plant foods had the same risk of dying from heart disease as people with the highest intake of red meat and other animal foods.

The main message from this study is clear.

  • Replacing red meat and other animal foods with plant foods can be a healthier choice, but only if they are whole, minimally processed plant foods like whole grains, fruits, vegetables, nuts, legumes, coffee and tea.
  • If the plant foods are refined grains, fruit juices, French fries and chips, sugar sweetened and artificially sweetened beverages, sweets and desserts, all bets are off. You may be just as unhealthy as if you kept eating a diet high in red meat and other animal foods.

A more subtle message from the study is that you don’t need to be a vegan purist to experience health benefits from adding more whole, minimally processed plant foods to your diet. The people in this study were not following some special diet. The only difference was that some of the people in this study ate more plant foods and others more animal foods.

For more details on the study, read the article above.

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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