Friday, July 13, 2018

Non-nutritive Sweeteners And Satiety

The Study
The GI system is believed to contain sweet taste receptors that have an important impact on satiety and hunger. In this interesting study, 12 healthy young men and women had each of the following preloads injected directly into their stomach on separate occasions: 1) 50 grams of glucose 2) 25 grams of fructose 3) 220 mg acesulfame-K, which is a non-nutritive sweetener. Visual analogue scales were used to rate subjective feelings of hunger and satiety. Compared to glucose and fructose, the non-nutritive sweetener initially caused a significantly stronger decrease in hunger and increase in satiety. However, this was followed by a significantly steeper return of hunger. American Journal of Clinical Nutrition 2018; 107:707.

Take Home Message
When I first started studying nutrition, the prevailing wisdom was that weight loss was all about calories in versus calories out. We now know that there is so much more to the story. A huge number of factors influence when and what we eat. Receptors in the GI system are now thought to play a big part. This is a fascinating study.  It utilizes my favorite study design, the crossover trial. In this type of study, each subject receives all interventions on separate occasions and acts as their own control. This really reduces the odds of residual confounding impacting the results. 

In this study, the artificial sweetener caused a significantly greater return to hunger when compared to the calorie containing sugars.  A diet soda or sugar-free dessert is a nice treat for those giving up sugar. However, it is a good idea to limit consumption of artificial sweeteners to just a few times per week. Daily use of non-nutritive sweeteners can have a dramatic effect on hunger and cravings for refined carbs. A few servings per week are not a problem, but daily consumption can really slow weight loss.

Sugar Consumption And Frailty

The Study
This study included 1,973 subjects from Spain over 60 years of age. Sugar consumption was measured with a computer based food frequency questionnaire. Frailty was defined as the presence of three of the following symptoms; exhaustion, low physical activity, slow gait speed, unintentional weight loss and muscle weakness. After several years of follow-up, subjects consuming the most sugar (greater than 36 grams or 9 teaspoons per day) had over twice the risk of frailty when compared to subjects consuming the least amount of sugar (less 15 grams or 4 teaspoons of sugar). American Journal of Clinical Nutrition 2018; 107:772.

Take Home Message
The research literature has shown that added sugar increases risk of obesity, type 2 diabetes, and heart disease. This study shows that it also may have a very negative impact on healthy aging. What makes this study interesting is that it focuses on quality of life and ability to function, rather than a single disease outcome. Do your very best to strictly limit sugar in your diet. Better yet, completely eliminate it.

Book Review: The Obesity Code

Next up for review is The Obesity Code: Unlocking The Secrets Of Weight Loss. The author, Dr. Jason Fung is a Canadian Nephrologist.

This book theorizes that overeating and a sedentary lifestyle have little to do with the obesity epidemic. Dr. Fung believes that obesity is caused by high levels of insulin. The book includes sections on the origins of the obesity epidemic, why overeating and exercise are not that important, Dr. Fung’s new model of obesity, what is wrong with our diet and the solution, which details when to eat and what to eat. The book is 315 pages long and very well written. I enjoyed reading it.

5 Things I Really Liked About The Obesity Code
1) Dr. Fung uses a lot of research to back up his claims. While he does make a few errors in interpreting the nutrition literature, this is a refreshing change in comparison to most best-selling weight loss books.

2) I agree that insulin levels have a lot to do with weight gain. This is a major reason why I recommend a low glycemic load approach for weight loss with my own clients.

3) I totally agree with the restriction on snacking. Even small amounts of extra calories consumed daily can add up to significant weight gain over time. Three balanced meals a day are all we need.

4) I totally agree that added sugars and refined carbohydrates are major causes of weight gain for most of us. Eliminating them needs to be a big part of any weight loss strategy.

5) I like the section on the importance of sleep in weight loss. The research is really beginning to back this up. Short sleep appears to decrease leptin levels and increase ghrelin levels. Both hormones have a lot to do with your ability to lose weight.

5 Things I Didn’t Agree With in The Obesity Code
1) I do not understand Dr. Fung’s theories on exercise. Here is an example:
Page 50: “Physical activity has virtually no relationship to the prevalence of obesity.”
Many studies show that physical activity is a big part of the strategy for those that are successful losing weight. A white paper on my website summarizes a number of these studies (you can find it here).

Page 51: “Exercise has not decreased since hunter gatherer times.” Does Dr. Fung really believe that a sedentary office worker that drives to work and sits in front of a computer all day gets as much physical activity as a caveman who had to walk everywhere he went and hunt and forage for every calorie he ingested?

Page 54: “Exercise has many benefits, but weight loss is not among them”. Strangely, right after this quotation, Dr. Fung cites a randomized trial showing that subjects who exercised 5 times per week lost an extra 10 pounds over 10 months when compared to those that did not exercise.

Generally, exercise by itself is not enough to hit your weight loss goals, but in combination with dietary change, exercise plays a critical role.

2) Similar to his view on cardio, this book makes absolutely no mention of the importance of resistance training. Lifting weights decreases the loss of lean body mass as we lose weight. This makes it much more likely that weight we lose will stay off. Building muscle with weight training increases metabolism. Each pound you add burns roughly 50 calories per day. Burning more calories per day makes it much easier to lose weight.

3) Dr. Fung believes that saturated fat is harmless. He recommends a regular consumption of butter, coconut oil, full fat dairy and beef tallow. He cites a reference from the Nurses’ Health Study to show that total fat is not associated with risk of heart disease (New England Journal of Medicine, 1997; 337:1491). While this is accurate, the rest of this study shows that the type of fat is very important. Saturated fit increased risk of heart disease in this cohort, while mono- and polyunsaturated fat decreased risk. Ironically, after citing this study, Dr. Fung says that saturated fat is fine and that vegetable oils have a negative impact on health. I am not quite sure how he mixed this up. Either way, saturated fat is to be avoided, it increases risk of heart disease.

4) I didn’t agree with the alcohol recommendations in The Obesity Code. Dr. Fung says up to 2 drinks a day are fine. It is my opinion that 14 drinks a week will seriously impede weight loss in both men and women. I have my clients cut down quite a bit on the alcohol if they are trying to lose weight.

5) This book recommends fasting 24 to 36 hours, two to three times per week. I don’t think this is a good idea. In the last year or so, I have blogged on 3 separate studies that examined fasting and were published in top journals. The results were not favorable. Among the findings:

-Drop out rates were higher in those fasting compared to more modest calorie restriction. This means it is much harder to stick to a fasting weight loss plan.

-There was no difference in weight loss between those fasting and those moderately restricting calories.

-LDL cholesterol significantly increased in subjects fasting.

-Several studies showed glucose dysregulation when fasting.

-Subjects fasting had an increase in inflammation.

-Subjects ate significantly more calories than normal the day after fasting.

-Energy expenditure decreased when fasting. 

(You can find these studies, here, here and here.) 

In The Obesity Code, Dr. Fung gives a number of tips when fasting.  Here are a few:

-Take cinnamon and eat chia seeds to reduce hunger.

-Drink salt water when you get dizzy.

-Take a magnesium supplement when you get muscle cramping.

-Drink salt water when you get headaches.

-Take Metamucil when you get constipated.

-Take a multivitamin because you won’t be getting any micronutrients on fasting days.

Maybe it’s just me, but having to do all of these things leads me to believe that fasting is neither a healthy or normal way for the human body to lose weight.

Is The Obesity Code Worth Reading?
Absolutely! It is important for me to read nutrition books that differ from my own personal philosophy. This book makes a lot of really good points. Levels of insulin have much to do with obesity. Limiting sugar and refined carbs are a huge part of the solution. Adequate sleep and limiting snacking are also big players. I would just add a bit to this good advice, notably; lift weights at least twice a week to build muscle, daily cardiovascular exercise is a huge part of weight loss, there is no need to fast, and lastly be sure to limit saturated fats and substitute them with more healthy vegetable fats.