Research Update: Mediterranean Diet Vs Low Fat Diet For Weight Loss

A Randomized Controlled Trial Of A Moderate Fat, Low Energy Diet Compared With A Low Fat, Low Energy Diet For Weight Loss In Overweight Adults
McManus K, et al.
International Journal of Obesity 2001 25:1503-11.

Objective: To compare the efficacy of a low fat diet and a moderate fat diet for long term weight loss.

Study Population: 101 overweight men and women (BMI between 26.5 and 46).

Methods: Subjects were randomized to one of two weight loss interventions.  Both diets had a goal of 1200 calories per day for women and 1500 calories for men.  Both diets provided 15-20% of calories as protein.  The low fat diet provided 20% of calories as fat and 60-65% of calories from carbohydrate.  The moderate fat diet provided 35% fat and 45-50% carbohydrate.

Everything else about the interventions was identical, including physical activity recommendations, behavior modification advice, weekly nutrition counseling sessions and the recording of food to gauge compliance.  Measurements included body weight, BMI, waist and hip circumference, physical activity and nutrient intake.  These were taken at baseline, 6, 12 and 18 months.

Results: 1) After 18 months, the moderate fat group had lost 9.2 pounds, decreased their BMI by 1.6 points and decreased their waist circumference by 2.7 inches.        2) During this same period, the low fat group gained 6.4 pounds, increased their BMI by 1.4 points and increased their waist circumference by 1 inch.  3) After 18 months, only 20% of the low fat group was actively participating in the weight loss program while 54% of the moderate fat dieters were sticking with their plan.

Discussion: This is a beautifully designed study.  First of all, it was 18 months long so you can assess both weight loss and maintenance of lost weight.  All elements of the weight loss interventions were identical, including total calories, total protein, physical activity and the dietary counseling component.  The only difference between the two interventions is that one was low fat, high carb and the other was moderate fat, moderate carb.

The results are striking.  After 18 months, the moderate fat group was 15.6 pounds lighter than the low fat, high carb group.  It is also notable that only 20% of the low fat dieters were able to stick to their program long term, while over 50% of the moderate fat dieters were able to stick to their program.  This is the knock on low fat diets in general.  Early on, you can lose some weight with them, but it appears that most weight is regained fairly quickly.  It seems that people have a hard time sticking to the low fat plans.  This is most likely due to the increased hunger caused by the dramatic swings in blood sugar on these diets.

Take Home Message: Fat is not the enemy, people.  When chosen wisely with vegetable source of fat, a moderate fat diet (35% of calories) can help reduce the risk of heart disease and diabetes and even help you maintain your weight.  Losing weight is great, but keeping it off is better.  The research is beginning to mount that a moderate fat diet gives you a better chance of keeping your weight off than a low fat diet.

Questions And Answers: Running

I always get a lot of questions on cardio in general and running in particular, so I thought running would make a great topic for my next Q and A.  As always, if you are initiating an exercise program, check with your doctor to make sure it is safe to do so.

Is running a good exercise for weight loss?

Yes and no.  As far as its effectiveness, running is great for weight loss.  You burn a ton of calories.  However, it is high impact and over time can be very tough on the body.  When we run, we put up to 6 times our body weight on our joints.  I’m about 190 lbs, so when I run, I’m pounding my knees, hips, back and ankles with the equivalent of over 1100 pounds of joint stress!  I don’t think our bodies were designed to deal with this level of impact, particularly if you run long distances multiple times per week.  I have found if someone runs long enough and far enough, year after year, they will surely have to deal with some major overuse injuries that can have a negative impact on their ability to engage in physical activity as they age.

I think I want to run a marathon, should I?

I always try to talk my clients out of running marathons.  I get the challenge and sense of accomplishment that goes with running one, but I just don’t think it’s safe.  I’ve already covered the joint stress issue.  Another issue is the effect of that amount of exercise on immune function.  The graph of exercise and immune function is J-shaped.  Your immune system starts to improve with increasing exercise.   However, after a point, immune function starts to decline with increasing exercise.  It even gets to a point below the baseline.  What that means is exercising too much can be worse for your immune system than not exercising at all.  Ever notice how most marathon runners get an upper respiratory infection after the race?  I’m not a fan of any activity that depresses immune function. 

What if I just love to run?

I’ve worked with enough clients over the years to know that running is really addicting and many people will do it despite my recommendation not to.  In this case I would suggest a modified run/walk program.  What I have them do is run for 2 minutes at a pace a little faster than normal and then follow this with 3 minutes of brisk walking.  This interval is repeated throughout the cardio session.  With this strategy, you get the increased calorie burn of running but also break up the impact of continuous running.

Do you advise your clients to run?

Never, I always try to talk them out of it.  If they persist I suggest the run/walk program described above.  I also let them know about lower impact forms of exercise like elliptical training.  This form of exercise will give you a similar calorie burn while protecting the joints. 

Book Review: The China Study

The China Study by Dr. T. Collin Campbell is next up for review.  Dr. Campbell is an accomplished researcher who is a Professor in Nutritional Biochemistry at Cornell University.  Dr. Campbell has published a ton of research papers and has served as a member on a number of government nutrition and health committees.  He is probably most well known for his work on the China Study, which is an ecological study of nutrition and disease among 6,500 people across China.  The focus of this book is what Dr. Campbell learned from the China Study.

Introduction

Dr. Campbell strongly believes that we should eat a very low fat, low protein diet devoid of all animal products.  If you read this blog regularly or have read my book, you know I am not a low fat or vegetarian guy.  In fact, I feel that low fat diets can have a negative impact on our health due to their resulting high glycemic load.  However, in the young field of nutritional epidemiology, I believe it is important to read work that goes against your own personal views to further understand the controversies that make this field so interesting and thought provoking.  The book presents a lot of Dr. Campbell’s research on nutrition and disease.  He then tells you what foods to eat, and goes into a detailed explanation of the problems with nutrition research and policy at both the academic and government level.  Overall the book was well written and an interesting read.

5 Things I Liked About The China Study

1) Points out the dangers of red meat and saturated fat.  One thing we have all learned from low fat diet advocates is that saturated fat and lots of red meat can be harmful.  This book is no exception.

2) Emphasis on fruits and vegetables.  Fruits and vegetables are the best things we can eat to improve our health.  This is stressed throughout the book.

3) Emphasis on whole grain foods.  While I’m not a high carb guy by any stretch, I realize the importance of whole grains in our diet.  The literature is teeming with evidence that whole grains improve our health and reduce risk of heart disease, stroke, diabetes and certain cancers.

4) De-empahsizes dairy products.  Those of you who know my writing know that I’m not a huge fan of dairy. 

5) Nutrition policy section  As a member of a number of government committees on nutrition policy, Dr. Campbell can relate his first hand experience on the competing interests of academia, the food industry, research science and the government’s influence on our food policy recommendations.  I found this section a very interesting read.

What I didn’t agree with in The China Study

1) This books groups all fats as unhealthy.  While certain fats are unhealthy (saturated fat and Trans fat) other fats like mono-unsaturated fat, poly-unsaturated fat and omega 3 fatty acids are extremely health promoting.  I don’t know why he didn’t differentiate the different classes of fats.

2) This book groups all animal proteins as unhealthy.  There is a very big difference in how chicken, salmon, turkey and egg whites treat our bodies when compared to steak, bacon and hot dogs.  Some animal proteins are bad for you and some are not.

3) Very high carbohydrate diets have recently been shown to have a negative impact on HDL cholesterol and triglycerides when compared to more Mediterranean style diets.  This isn’t mentioned anywhere in the book.

4) Very high carbohydrate diets result in a high dietary glycemic load.  The glycemic load has been associated with a variety of diseases in the past 10 years.  There was no mention of this anywhere in the book or even of the glycemic load as a concept.

5) His criticism of the Nurse’s Health Study was baffling.  He feels that NONE of the research out of Harvard tells us anything because of flaws in the design of the study.  I had a hard time understanding this argument.  His study is ecological in nature, follows 6,500 Chinese citizens and measures diet one time via a 3 day food record and he has total confidence in the results.  The Nurses’ Health Study is a prospective cohort study, follows 120,000 American nurses for over 30 years and measures diet by means of a validated food frequency questionnaire that is updated every 4 years to reflect changes in diet.  Every aspect of the Nurses’ Health Study is superior to the China study yet it is given no respect in this book. 

Is The China Study Worth Reading?

Absolutely.  I enjoyed the book and learned a lot.  At the end of the day, low fat diet advocates taught us a lot about a healthy diet: the dangers of saturated fat, red meat and dietary cholesterol as well as the benefits of fruits, vegetables and whole grains.  However, well designed research has added a lot to our understanding about the benefits of healthy fats, lean animal proteins, fish and other sources of omega 3’s and most importantly, a low glycemic load diet.