Thursday, July 14, 2011

Research Update: Individual Foods And Weight Gain

Changes In Diet And Lifestyle And Long-Term Weight Gain In Women And Men
New England Journal Of Medicine 2011; 36:2392-404.

Objective: To examine the impact of individual foods on weight gain over 20 years.

Study Population: 120,877 U.S. men and women from 3 separate cohorts, The Nurses’ Health Study, The Health Professional Follow-up Study and The Nurses’ Health Study II.

Methods:  Subjects were followed for approximately 20 years (20 years for the Health Professional Follow-up subjects and Nurses’ Health cohort and 12 years for the Nurses’ Health II cohort).  The impact of different foods and lifestyle factors on long term body weight was computed statistically.
Results:  Subjects gained an average of 3.35 pounds every 4 years for a total of 16.8 pounds over 20 years.  Weight gain was most associated with consumption of potato chips (1.69 pounds over 4 years for each daily serving), potatoes (1.28 pounds over 4 years for each daily serving), sugar sweetened beverages (1.0 pound per daily serving), red meat (.95 pound per daily serving) and processed red meat like bacon, pepperoni, etc (.93 pound per daily serving).
Conversely, weight loss was most associated with yogurt consumption (-0.82 lbs over 4 years per daily serving), nuts (-.57 pound per daily serving), fruits (-.49 pound per daily serving), whole grains (-.37 pounds per daily serving), and vegetables (-.22 pounds per daily serving).
Results were also reported for lifestyle factors: physical activity was associated with weight loss, while alcohol consumption, watching too much TV and sleeping more than 8 hours and less than 6 hours were all associated with weight gain.
Discussion: This is a very well designed study.  If you need evidence of this, you just have to look at the journal that it appears in.  The New England Journal of Medicine is the holy grail of medical research. 
Just about all of the foods that promoted weight gain were high glycemic load, refined carbohydrates and just about all the foods that promoted weight loss were low glycemic load foods.  I have found this to be absolutely true in my weight loss practice.  High glycemic load carbs cause a reactive hypoglycemia in most people that dramatically increases hunger a few hours after consumption.  The high insulin levels these foods promote may also favor fat storage.

Another thing that jumped out at me while reading this paper is the idea that even tiny changes in our diet can have dramatic impacts on our long term weight.  If you have an additional 75 calorie snack each day, this will actually add up to a gain of almost 8 pounds per year and over 23 pounds in 3 years!  This is a big reason why I have my clients eliminate snacking and, of course, strictly limit the high glycemic load carbs.

Take Home Message: If weight loss is your goal, you need to understand the concept of glycemic load.  This study provides even more evidence of the weight gaining effects of high glycemic carbs. 

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