Wednesday, August 10, 2011

Better to Eat Your Carbs at Night? - Dr. O's Analysis

I.   Introduction 
II.  Experimental Design
III. Results
IV. Conclusion
V.  References
I.  Introduction

This article is a perfect example of why it is important to ALWAYS seek new knowledge.  However, it’s also an example of how some research papers do not COMPLETELY support their hypothesis and leave reasonable doubt.  People, it's not just about the title and the abstract!!  I've read multiple reviews of this paper, and everyone is claiming this is the best strategy.  HOLD ON!!  The results aren't that clear.  I'll give you a clue, the title of this journal article starts with "Greater Weight Loss...", not "Greater Fat Loss..."

In regards to healthy eating, one of the common rules of thumb is to "eat low glycemic carbs throughout the day and avoid carbs at night".  I think everyone would agree that this practice is much better than eating high glycemic, refined carbs.  It promotes the maintenance of a healthier and leaner body.  But when it comes to fat loss, can it get better?  In other words, if you are keeping carbs in your diet, is eating low glycemic carbs throughout the day the best strategy for losing fat?  The following article challenges this theory and suggests that it may not be.

A study by Sofer et al. (2011) was conducted to investigate the effects of eating carbohydrates mostly at dinner on a variety of health parameters.  The authors’ theory behind this diet is that with a single daily insulin secretion (from carb intake) at dinner, there would be a higher concentration of leptin (a.k.a. - the satiety hormone) in the body beginning 6-8 hours later (the next morning and throughout the next day), potentially reducing hunger throughout the day.  
II.  Experimental Design

78 police officers were divided into two diet groups.  Each diet was “a standard low-calorie diet (20% protein, 30–35% fat, 45–50% carbohydrates, 1,300–1,500 kcal)”.  The control diet distributed carbohydrate intake throughout the day while the experimental group had most of their carbs at dinner.  The following diet programs were followed for 6 months:
Sofer et al., 2011 - Experimental and Control Diets followed for 6 months
III.  Results

     A.  Physical Changes
 After 180 days, both diets resulted in significant reductions in weight, BMI, abdominal circumference, and body fat percentage.  The experimental diet resulted in greater reductions in all of these parameters than the control diet; however, only weight loss was significantly greater in the experimental diet group than the control group (…raises eyebrow…).

     B.  Hunger-Satiety Questionnaires 
Subjects also completed Hunger-Satiety questionnaires (HSQs), which consisted of descriptions “ranging from starving (1 point) to devastatingly full (10 points)”.  HSQs were filled out at 8a, 12p, 4p, and 8p on day 0, 7, 90, and 180.  Higher questionnaire scores correlate to greater satiety and less hunger.  By day 90, experimental group HSQ values were significantly higher than the control group at noon and afternoon.  By day 180, experimental group HSQ values were significantly higher than the control group at noon, afternoon, and at night (…slightly lowers eyebrow…just slightly).

     C.  Biochemical Factors
Changes in the following biochemical factors were also analyzed:

Insulin: Both the control and experimental diet resulted in a significant decrease in insulin levels by day 180 (compared to day 0).  However, insulin levels were significantly lower in the experimental diet group.

Fasting Glucose: The experimental diet also resulted in significantly lower fasting glucose levels at day 180 when compared to day 0 (20% decrease).  The control diet decreased fasting glucose levels, but the change was not statistically significant (8.3% decrease).

Cholesterol:  Both diets resulted in similar decreases in LDL-cholesterol concentration at day 180 (experimental = 9.7%; control = 7.6%).  However, the experimental diet resulted in a significantly greater increase in HDL-cholesterol concentration at day 180 (experimental = 40.8%; control = 26%).

Leptin: Leptin concentrations decreased significantly in both groups by day 90 and 180.  However, there was no significant difference in this decrease between control and experimental diets.

Adiponectin (regulates lipid and glucose metabolism; more is better): The experimental diet resulted in a significant increase in avg. 12-h adiponectin concentrations at day 180 as compared to day 0 (43.5%).  The control diet increase was insignificant (13.9%).
IV. Conclusion 

This article suggests that eating most of your carbs at night is more beneficial for decreasing hunger and improving certain biochemical factors.  However, it is still unclear whether the experimental diet results in greater reductions of physical factors such as BMI, abdominal circumference, and body fat percentage (due to the lack of statistically significant differences in data).  The experimental diet only resulted in significantly more weight loss, which may include both muscle and fat.  Also, there was no difference in changes in leptin concentrations between the experimental and control diets, which disproves the authors’ leptin hypothesis.  This issue may have been cleared up if the authors had a better diet protocol.

Subjects maintained “a standard low-calorie diet (20% protein, 30–35% fat, 45–50% carbohydrates, 1,300–1,500 kcal)”.  However, one of the most common recommendations for maintaining muscle and losing fat is to increase protein intake.  Many personal trainers and nutritionists recommend a low-calorie diet consisting of 30% protein, 40% carbs, 30% fat.  Furthermore, people that follow a Paleo, low-carb, or ketogenic diet may eat even more protein and less carbs.  Therefore, a diet with 45-50% of calories from carbohydrates may be an issue, no matter what time of the day you eat them.  If I were to conduct a follow up study, I would lower this carb intake.  Nonetheless, this article does raise some interesting questions about the status quo.
V. References

1.    Sofer, S., et al., Greater Weight Loss and Hormonal Changes After 6 Months Diet With Carbohydrates Eaten Mostly at Dinner. Obesity, 2011. 48: p. 1-9.


Nnamdi D'Elephant said...

Great article. I don't understand why a whole study had to be conducted about when is the best time to eat carbs. I mean to achieve "weight" loss it is as simple as calories in vs. calories out...duuhh lol. Im 200 lbs and if i wanted to get to 185lbs I could eat carbs at 2am in the morning & it would not matter as long as I stayed under my total caloric limit for the day. I wish this study addressed a new innovative "fat-loss" regime *sigh

Tim said...

the study doesnt mean its better to eat carbs at night. instead of having an insulin response all day from spreading it out during the day they kept it 2 just 1 time which is probably why they benefited. I bet the results would have been even better if they would of had all their carbs around lunch and protein and fats for the other meals since insulin sensitivity is at its best during the day

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