Tuesday, March 27, 2012

Using Protein for Weight Loss and Muscular Improvement

In my last blog, I mentioned that the tail end of my weight loss was partly due to increasing protein intake [1].  This idea came from the results of a few studies I reviewed recently.  As most people would guess, protein helps improve muscle mass, but it also has key effects on fat loss.  Exactly what does the protein do?  How much should you consume?  Keep reading.

Effects of a High Protein Diet

  1. Higher Total Weight/Fat Loss: Subjects who strength trained and ate one-third of their calories from protein lost 12.7% of their total body weight and about 25 lbs. of fat in a 16-week study [2]. In the same study, subjects who strength trained and ate about one-fifth of their calories from protein lost 10% and about 18 lbs.  Both groups were on a low calorie diet and consumed about the same total amount.  Another study compared a carbohydrate:protein ratio of 1:1 versus a ratio of 3:1 (more carbs, less protein) in combination with a circuit training routine of strength and aerobic exercises for obese/overweight women over 12 weeks [3].  All diets were designed to create a 500 calorie deficit.  The group that ate more protein and less carbohydrates lost over 15 lbs. vs. 8.8 for the lower protein/higher carb group.  A third study, this one also with obese women, looked at an exercise routine of walking and strength training in combination with differing amounts of protein and carbohydrates[4].  The high protein group (102 grams of protein and 127 grams of carbs per day) vs. a high carb group (57 and 202).  The amount of calories and fat consumed were very similar.  The high protein group lost the most weight and, by far, the most fat (about 19 lbs).  (Note: the studies mentioned in this paragraph mainly involve differing amounts of protein.  However, carbohydrates and fat vary in each of the studies to ensure equal caloric intakes, so it cannot be said with certainty that protein is mainly responsible for the changes discussed).
  2. Optimal Muscle Growth: This may be obvious, but protein allows for your muscles to grow to their optimal level.  If you are not consuming enough protein to meet your needs, muscle growth in response to strength training will be limited [5].  
  3. Muscle Retention During Weight Loss: Not only does a higher protein intake lead to greater weight loss, but it also leads to better retention of lean mass (i.e. muscle) [4,5].  Think of this in terms of your own weight loss goal (if this is a goal of yours): do you want to lose both muscle and fat, so you'll be leaner but with the same muscle "tone" that you currently have?  Or...do you want to retain your muscle and mainly lose fat, leading to both a leaner and more muscular appearance?  Every time I have posed this question to new clients, they have chosen the latter scenario. 
Recommended Intake 

Intakes are generally recommended in terms of kilograms of body weight.  To calculate your weight in kilograms, divide your weight in lbs. by 2.2.  As for how much you should be taking, one research review suggests consuming 1.2-1.8 grams per kilogram of body weight per day [6].  Another study found 1.4 grams per kilogram of body weight per day to be sufficient [5].  These recommendations are for individuals who are active, especially those who strength train (I will not discuss recommendations for sedentary individuals since I don't believe sedentary is a natural or healthy state).  Using 1.4 grams per kg. per day as a minimum, here is what it looks like for 100, 150, and 200 lb individuals:
  • 100 lb. person = 45.5 kg.  Recommended Intake (RI): At least 64 grams per day.
  • 150 lb. person = 68.2 kg. RI: At least 96 grams per day.
  • 200 lb. person = 91 kg. RI: At least 128 grams per day.
Honestly, I think even these recommendations are low, but research has shown 1.4 to be as effective as 2.4 grams per kg. per day in aiding the growth of muscle (5).

Protein: Final Notes 

While 1.4 grams can serve as a minimum for the general population, some populations need even more protein to avoid deficiency/muscle wasting.  Some of these populations are people on low calorie diets, those starting a strength training routine, vegetarians, elderly, and people with eating disorders [6]. 

A major reason why increasing protein likely leads to weight loss has to do with its general inability to support the process of storing fat.  Only two amino acids (leucine and lysine) could support a meaningful amount of conversion to fat [5].  Therefore, excess protein is generally broken down for other uses or just excreted out of the body through urine. 

With all of this in mind, I support increasing protein intake to help with weight loss, muscle retention during weight loss, or muscle gain when calories aren't restricted.  Greater amounts of protein can be taken in through eating more red meat, poultry, fish, or eggs at each meal.  All of these provide about seven grams of protein per ounce/egg.


Naureen said...

This was a great read!

Dr. Sean Preuss said...

Thank you Naureen!