Pea_on_plate_imagePart I of a 4-part series on metabolism and weight loss.

What dietary approach is best for weight loss?

Your coworker says, “Weight Watchers rocks…I lost 30lbs and I feel great!”

Your friend says, “I just took out all breads and lost 10lbs in a week!”

Your mom says, “Low carb is the way to do it.”

It is quite difficult to know what to believe these days. We are in an age of information-overload and it seems everyone wants to give us their 2-cents on what we should or shouldn’t eat to lose weight. There are thousands upon thousands of weight loss books on the market all claiming to offer The Ultimate Solution! So, what is the “best” plan?

Let’s dig into the nitty-gritty here to search for the truth to this question! 

While I can’t possibly review every diet out there, I’ll start with some of the more popular approaches. Very low calorie diets (VLCDs), ketogenic diets, intermittent fasting (IMF) and meal timing, and various macronutrient profiles (i.e. Zone, Atkins, and Ornish diets) are some of more well known diets.  What are they and more importantly…do they work?

1.Very Low Calorie Diets (VLCDs):

What is it?

  • Diets that restrict daily calorie intake to <800 per day with ~70-100g of protein, typically consumed in liquid form (protein shake)
  • It is intended for rapid weight loss of >3lb per week
  • It should ideally be completed under medical supervision for <16 weeks due to possible side effects including gallstones, cardiac arrhythmias, and electrolyte imbalances
  • Examples: LiveLyte, HCG diet, OptiFast, Medifast

What does the research say? 

  • There are conflicting reports, but these diets may produce higher incidence of binge eating once the diet is completed
  • VLCDs typically produce rapid weight loss over first 1-2 weeks, then slower weight loss with a maximum loss achieved at 6-months, then a gradual weight regain over time
  • They usually have poor adherence
  • Patients typically lose half of the weight that may be expected based on the calorie level

My conclusion?

  • These diets are for very specific individuals with an urgent, medically necessary reasons to lose weight. Those who follow these plans should be closely monitored by a health professional and should follow the diet for short-term use only. Appropriate follow up at the end of the plan with a dietitian or health coach is necessary.

2. Ketogenic Diets (KD):

What is it?

  • High fat (>70% of total calories), adequate protein (1.2-1.5g/kg ideal body weight), and very low carbohydrate diet (<50g/day or <10% of total calories)
  • During ketosis, the body primarily uses ketones as its energy source as opposed to glucose
    • Ketones are produced in the liver. Acetoacetate, beta-hydroxybutryric acid, and acetone are all ketones
    • Ketones can be measured in blood, urine and breath. Typically, ketosis causes “fruity breath.”
  • Ketosis is different than diabetic ketoacidosis and is typically thought to be safe, but may not be an appropriate diet for all populations

What does the research say?

  • A meta-analysis of 13 studies including 1577 individuals compared ketogenic diet in the long-term management (1-year) of obesity compared to a low fat diet (Bueno, 2013)
    • KD achieved greater reductions in body weight compared to a low fat diet of the same calorie level
      • This may be due to its ability to modulate energy expenditure, reduce insulin levels, and/or enhance satiation (feelings of fullness), but the exact mechanism is not fully understood
    • Differences in weight loss are of little clinical significance although statistically significant
    • Long-term adherence to the ketogenic diet in all studies was poor, and best results were found within the first 6-months on the diet  

My conclusion?

  • If you are experiencing very stubborn weight loss and feel ready for a new approach, then short-term use (<6-months) of the ketogenic diet may offer you some relief. However, the weight loss effects are probably mild. It is a very challenging diet to stick to and is particularly tough in social situations. It can take up to a few weeks for the body to fully adapt to ketosis and during that time you may experience extreme fatigue, brain fog, cravings, and even flu-like symptoms. Ketogenic diets may offer additional health benefits outside of weight loss that are not discussed in this article. 

3. Intermittent Fasting (IMF) & Meal Timing:

What is it?

  • IMF is restricting food intake during certain periods of time during the day or the week
    • Example: fast for 16-hours per day, consume meals during an 8-hour window (10am-6pm)
    • Example: calorie restriction 2 days per week, normal calorie diet 5 days per week
  • Meal timing refers to the amount of meals/snacks consumed each day and the amount of time spaced between them
    • Example: 3 meals per day, no snacking
    • Example: 6 mini-meals per day

What does the research say?

  • Those with night eating syndrome, meaning most calories are consumed at night with subsequent morning anorexia, are more likely to be over weight
  • Behaviors associated with prevalence of obesity include skipping breakfast and eating dinner away from home 
  • According to the National Weight Control Registry, those who have successful weight loss and weight maintenance typically consume breakfast
  • The number of meals consumed daily has not been subject to rigorous scientific investigation
  • Slower eating, more chewing, and longer mealtimes may be important strategies to develop satiety and utilize more calories (due to burning calories during chewing!). However, the studies on actual weight loss outcomes are inconsistent 
  • Intermittent energy restriction (VLCD on 2 consecutive days per week and normal calorie diet 5 days per week) was found to be as effective as continuous energy restriction (25% calorie restriction below needs 7 days per week) with regard to weight loss (Harvie, 2011)
  • Muslims who fast during the month of Ramadan from sunrise to sunset generally do not lose weight or decrease calories they consume in a day

My conclusion?

  • IMF may be a helpful strategy for individuals who do not wish to adhere to a daily calorie restriction when attempting to lose weight. Using the protocol of 2 days of a VLCD (<800 calories per day) and 5 days of normal eating will allow you to lose as much weight as someone who mildly restricts calories every day of the week. In general, fasting is not an effective weight loss strategy, but may offer health benefits that this article does not address. 
  • On the topic of meal timing, there is only association data that eating more calories during the beginning of the day and less calories at the end of the day is effective for maintaining a healthy body weight.  Generally, people have success with weight loss and weight maintenance when they consume breakfast daily and avoid eating heavy meals late at night. 

4. Macronutrient Profiles:

What is it?

  • Macronutrients are nutrients that contribute calories to the diet and include carbohydrates, proteins, and fats
  • It is speculated that genetics probably determines what proportion of protein, fat, and carbs works best for the person in context of a reduced calorie diet
  • The typical American diet consists of 50% carbohydrate, 35% fat and 15% protein
  • Various popular weight loss diets modify the macronutrient ratios:
    • Atkins- very low carbohydrate 
    • Zone- 40% carbohydrate, 30% fat, 30% protein
    • Ornish- very low fat, high in carbohydrates

What does the research say?

  • The A to Z Weight Loss Study: A Randomized Trial
    • Compared Atkins, Zone, Ornish, and LEARN diets in 311 free-living overweight, non-diabetic and premenopausal women
    • At 12-months: Atkins diet lost ~4.7kg v other diets lost ~1.6-2.6kg
      • However, the study did not assess dietary adherence to the 4 different diets 
  • 811 overweight adults assigned to 1 of 4 diets with varying macronutrient profiles (similar food choices), followed over 2 years (Sacks, 2009)
    • At 6-mo each diet group lost ~6kg, but began to regain weight after 12-mo.
    • Weight loss with attendance at group support sessions yielded the best results 
    • Satiety, hunger, and satisfaction with the diet was similar for all groups.
  • Overall dietary adherence rates were low.

My conclusion?

There may be some mild benefit regarding weight loss in consuming a lower carbohydrate diet. However, the optimal level of carbohydrate restriction is not established. One can expect to lose weight just by sticking to a diet, rather than worrying about the actual details of the diet itself. Sticking to any diet is key and helps with weight loss!

Stay tuned for Part II of this 4-part series on metabolism and weight management where I’ll review the effectiveness of popular weight loss supplements. 

References:

  1. Harvie MH, et al. The Effects of Intermittent or Continuous Energy Restriction on Weight Loss and Metabolic Disease Risk Markets: A Randomized Trial in Young Overweight Women. International Journal of Obesity. 2011;35:714-727.
  2. Azevedo FR, Ikeoka D, and Caramelli B. Effects of Intermittent Fasting on Metabolism in Men. Rev Assoc Med Bras. 2013;59(2):167-173.
  3. Ynsheng MA, et al. Associations Between Eating Patterns and Obesity in a Free-living US Adult Population. Am J Epidemiol. 2003;158:85-92. 
  4. Sylvia Karasu, M.D., T. Byram Karasu, M.D.; The Gravity of Weight; 1st; 1585623601; American Psychiatric Publishing; 01/01/2010; R2 OnLine Library.
  5. G.E. Mullin et al. (eds.), Integrative Weight Management: A Guide for Clinicians, Nutrition and Health, DOI 10.1007/978-1-4939-0548-5_19, Springer Science + Business Media New York 2014.
  6. Gardner CD, et al. Comparison of the Atkins, Zone, Ornish and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premeopausal Women The A TO Z Weight Loss Study: A Randomized Trial. JAMA. 2007;297:969-977.
  7. Sacks FM, et al. Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates. N Engl J Med. 2009;360:859-873.
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