Archive | October, 2015

All About Probiotics

15 Oct

By Tim Skwiat, MEd, CSCS, Pn2

What Are Probiotics?

According to the International Scientific Association for Probiotics and Prebiotics (ISAPP), probiotics are defined as “living microorganisms that, when administered in adequate amounts, confer a health benefit on the host.”1

The digestive tract alone contains roughly 100 trillion bacteria. To put that into perspective, we have 10 trillion cells that make up our bodies. In other words, the bacterial ecosystem that makes us who we are outnumbers our cells on the order of 10 to 1. From a DNA perspective, the genes of the microbes that inhabit our bodies exceed the amount of human DNA we each have by a factor of 100.

small world

Cani PD, Delzenne NM. Pharmacol Ther. 2011;130(2):202-212.(2)

Building and maintaining a healthy gut flora—which involves optimizing the balance of “good” to “bad” bacteria—is critical to digestive system health and function, overall health, immune system function, mental health and wellbeing, metabolism and weight management, respiratory (i.e., lungs) and integumentary (i.e., skin) systems, and more. When the gut flora is at a healthy balance, it provides immense support to digestive function, immune system, metabolism, skin health, mental wellbeing, and more.

However, when the gut is unbalanced and unhealthy, a number of issues can ensue. In fact, research suggests that having inadequate levels of healthy bacteria in your gut may contribute to over 170 different health issues, including weight gain and difficulty with weight management, as well as digestive-, skin-, and mental wellbeing-related issues. Along these lines, there are many common factors that can upset the balance of gut bacteria, including:

  • Aging
  • Environmental factors
  • Food choices (e.g., Certain artificial sweeteners like sucralose have been shown to reduce the levels of beneficial bacteria in the gut and negatively alter the gut flora.11)
  • Stress
  • Medications (e.g., antibiotics12)
  • Smoking

In other words, a modern lifestyle—characterized by poor food choices, stress, and antibiotics, as well as factors outside of your control like nutrient-deplete soil, environmental toxins, and pollutants—can wreak havoc on the gut flora. The great news that there is a solution to an unhealthy gut, and you can begin restoring your gut health by supplementing with high-quality probiotics.

western living

Adapted from Schippa S, Conte M. Nutrients. 2014;6(12):5786-5805.(5)

This leads us into a discussion of how probiotics may be helpful. In the GI tract, probiotics serve a number of important functions, as they:

  • Support a balance of healthy bacteria in the gut
  • Keep pathogenic bacteria from settling and growing
  • Help digest and absorb nutrients and support a healthy GI tract
  • Help regulate and support a healthy immune system
  • Produce key nutrients (e.g., B & K vitamins, short-chain fatty acids)
  • Keep the system moving
  • Help metabolize chemicals and phytonutrients
  • Synthesize polyamines
  • Produce coagulation and growth factors
  • Promote a healthy balance of cytokines
  • Regulate secretion and use of intestinal mucus
  • Help regulate blood flow to internal organs
  • Provide gut barrier reinforcement
Hill C, Guarner F, Reid G, et al.(1)

Hill C, Guarner F, Reid G, et al.(1)

A Lesson in ProBiology

Symbiosis refers to a “mutually beneficial relationship between two different organisms living in close approximation.” Pertinent to the conversation on probiotics, humans have evolved intimate symbiotic relationships with gut microbes. In fact, human beings can be considered “superorganisms” as a result of their close symbiotic associations with the gut microbiota.3 Optimal human health and homeostasis revolves heavily on this symbiotic relationship, which entails maintaining a healthy balance of bacteria in the gut.

Along these lines, dysbiosis refers to microbial imbalances on or within the body. In other words, dysbiosis describes the state of an unhealthy imbalance of bacteria in the gut flora, characterized by excessive levels of pathogenic bacteria, inadequate amounts of commensal and probiotic bacteria, and/or reduced bacterial diversity. Fundamentally, gut dysbiosis destroys the symbiotic relationship between humans and microbes; in fact, gut dysbiosis has been linked to numerous human health issues, including obesity.4–9

This is leads into why probiotics are critical to restoring gut health and fortifying the gut microbiome. By their very definition, probiotics are non-pathogenic, healthy bacteria that confer a clear beneficial effect on the host (i.e., humans). Supplementation with these commensal bacteria—which supply essential nutrients and defend against pathogens—helps restore a normal, healthy microbiome. Beyond restorative and reactive measures, probiotics help to prevent a normal, healthy individual from acquiring dysbiosis in the future.

In both cases, probiotics promote probiosis (i.e., an association of two organisms that enhances the life processes of both) and support and fortify the symbiotic relationship between humans and gut microbes.

The symbiotic relationship between humans and gut bacteria. Commensal bacteria supply the host with essential nutrients and defend the host against opportunistic pathogens. They are involved in the development of the intestinal architecture and immunomodulatory processes (i.e., healthy immune system function). On the other hand, the host provides the bacteria with nutrients and a stable environment.(10)

The symbiotic relationship between humans and gut bacteria. Commensal bacteria supply the host with essential nutrients and defend the host against opportunistic pathogens. They are involved in the development of the intestinal architecture and immunomodulatory processes (i.e., healthy immune system function). On the other hand, the host provides the bacteria with nutrients and a stable environment.(4)

What Does This Mean for You?

Building and maintaining a healthy gut flora—which involves optimizing the balance of “good” to “bad” bacteria—is critical to digestive system health and function, overall health, immune system function, mental health and wellbeing, metabolism and weight management, respiratory (i.e., lungs) and integumentary (i.e., skin) systems, and more. When the gut flora is at a healthy balance, it provides immense support to digestive function, immune system, metabolism, skin health, mental wellbeing, and more.

However, research suggests that having inadequate levels of healthy bacteria in the gut may contribute to over 170 different health issues (including weight gain and difficulty with weight management), and a modern lifestyle characterized by stress, processed foods, sugar, artificial sweeteners, antibiotics, nutrient-deplete soil, and environmental toxins can wreak havoc on the gut flora and disrupt the natural balance of healthy bacteria.

With that in mind, I would consider a high-quality probiotic (recommendation: BioTrust Pro-X10) “foundational” for nearly everyone to support optimal levels of probiotics, establish and maintain a healthy balance of bacteria in the gut, promote a healthy digestive system, and support a robust immune system. Along with probiotic supplementation, you can also fortify your gut by eating plenty of traditionally fermented foods:

  • Kefir, yogurt
  • Sauerkraut, pickles, and other properly fermented vegetables
  • Miso, tempeh
  • Kombucha
  • Red wine

Establishing optimal gut health is a balance between what’s there and what’s not there. Along those lines, it’s also advised to be mindful of and reduce exposure to the controllable factors (e.g., diet, stress, medications) that may negatively impact the composition of the microflora, gut health, and every other aspect of human health and function mentioned above.

References:

  1. Hill C, Guarner F, Reid G, et al. Expert consensus document: The International Scientific Association for Probiotics and Prebiotics consensus statement on the scope and appropriate use of the term probiotic. Nat Rev Gastroenterol Hepatol. 2014;11(8):506-514. doi:10.1038/nrgastro.2014.66.
  2. Cani PD, Delzenne NM. The gut microbiome as therapeutic target. Pharmacol Ther. 2011;130(2):202-212. doi:10.1016/j.pharmthera.2011.01.012.
  3. Li M, Wang B, Zhang M, et al. Symbiotic gut microbes modulate human metabolic phenotypes. Proc Natl Acad Sci. 2008;105(6):2117-2122. doi:10.1073/pnas.0712038105.
  4. Martín R, Miquel S, Ulmer J, Kechaou N, Langella P, Bermúdez-Humarán LG. Role of commensal and probiotic bacteria in human health: a focus on inflammatory bowel disease. Microb Cell Factories. 2013;12(1):71. doi:10.1186/1475-2859-12-71.
  5. Schippa S, Conte M. Dysbiotic Events in Gut Microbiota: Impact on Human Health. Nutrients. 2014;6(12):5786-5805. doi:10.3390/nu6125786.
  6. Ley RE, Turnbaugh PJ, Klein S, Gordon JI. Microbial ecology: Human gut microbes associated with obesity. Nature. 2006;444(7122):1022-1023. doi:10.1038/4441022a.
  7. DiBaise JK, Frank DN, Mathur R. Impact of the Gut Microbiota on the Development of Obesity: Current Concepts. Am J Gastroenterol Suppl. 2012;1(1):22-27. doi:10.1038/ajgsup.2012.5.
  8. Turnbaugh PJ, Hamady M, Yatsunenko T, et al. A core gut microbiome in obese and lean twins. Nature. 2009;457(7228):480-484. doi:10.1038/nature07540.
  9. Zhang H, DiBaise JK, Zuccolo A, et al. Human gut microbiota in obesity and after gastric bypass. Proc Natl Acad Sci U S A. 2009;106(7):2365-2370. doi:10.1073/pnas.0812600106.
  10. Ridaura VK, Faith JJ, Rey FE, et al. Gut microbiota from twins discordant for obesity modulate metabolism in mice. Science. 2013;341(6150):1241214. doi:10.1126/science.1241214.
  11. Abou-Donia MB, El-Masry EM, Abdel-Rahman AA, McLendon RE, Schiffman SS. Splenda alters gut microflora and increases intestinal p-glycoprotein and cytochrome p-450 in male rats. J Toxicol Environ Health A. 2008;71(21):1415-1429. doi:10.1080/15287390802328630.
  12. Jernberg C, Lofmark S, Edlund C, Jansson JK. Long-term impacts of antibiotic exposure on the human intestinal microbiota. Microbiology. 2010;156(11):3216-3223. doi:10.1099/mic.0.040618-0.
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Move More, Eat MORE

7 Oct

By Tim Skwiat, MEd, CSCS, Pn2

When it comes to fat loss, it’s quite common to hear the adage, “Move more, eat less,” which stems from the fundamental principle of physiology, nutrition, and metabolism that states:

In order to lose weight, one must consume fewer calories than s/he burns—on a regular basis, consistently over time.1

Simply put, this is saying that a calorie deficit is necessary (over time) for meaningful fat loss. As simple and straightforward as that is, it’s neither easy nor particularly useful. Just ask anyone who’s attempted to lose weight through a reduced-calorie diet (i.e., eat less). For the overwhelming majority of folks, it’s not sustainable. In fact, researchers estimate that fewer than 25% of folks who lose weight are successfully able to keep it off for at least a year.2

While human physiology complies with the first law of thermodynamics, the “move more, eat less” axiom takes into consideration only a narrow aspect of the weight management equation. That is, there’s more to the story than the “numbers game” (i.e., counting calories) including a variety of environmental and behavioral factors.3

In other words choice to eat food can be sparked by metabolic need, hedonic drive (i.e., the “food reward system”), or a combination of the two. In today’s world, we no longer eat only when we’re “metabolically hungry.” Instead, we are driven to eat even when we’re not truly hungry and despite having vast energy reserves (i.e., body fat).

More and more, obesity researchers are investigating the impact of hedonic drive and other factors, which involves cognitive, reward, and emotional aspects, and may include choosing to eat based on food environment, food addiction, stress relief, boredom, and mood elevation.4

For example, think about a time when you ate (or drank) something because you felt that you “deserved” it, whether that was after a tough workout or a stressful day at the office. You weren’t necessarily hungry, but you made up your mind that you “earned” that reward. Another example of hedonic eating is susceptibility to food environment cues. Think back to a time when you ate something “because it was there.” Ever happen to you?

All of that is meant to create awareness that the “Move more, eat less” approach to fat loss, while “accurate,” may not be all that utilitarian or encompassing. In other words, from a well-educated fitness professional, it’s not very articulate or useful advice. However, there is truth to it, but does it tell the whole story?

Move More, Eat More

It’s no secret that most people could stand to move more. Generally speaking, research suggests that lack of physical activity is a significant determinant of the overall rise in obesity amongst adults and adolescents.5,6 Not surprisingly, people who are “normal weight” typically engage in more moderate and vigorous physical activity compared to overweight and obese folks.7

With little to debate about the energy expenditure portion of the equation, what about eating more? That seems to violate the law of thermodynamics and the age-old proverb about eating less, right?

Yes and no. Again, there’s no discounting the energy balance equation; the current body of scientific research suggests that this is necessary to lose fat. However, eating fewer calories (which can be viewed as “eating less”) doesn’t necessarily have to mean eating less food. In fact, studies show that it’s possible to eat significantly more food and lose substantially more fat.

That is, you don’t necessarily need to rely on the “numbers game” to achieve and maintain your ideal body composition. You see, research suggests that people may not limit what they consume based on calories alone. Specifically, feeling full (i.e., satiety) is a major reason that people stop eating. In other words, rather than the calorie content of food, the volume (i.e., weight, amount) of food that is consumed at a meal is what makes people feel full and stop eating.8

In fact, research strongly suggests that how much you eat daily is regulated by the weight of the food rather than by a certain number of calories. Researchers from Penn State have posited that “energy density is a key determinant of energy intake in that cognitive, behavioral, and sensory cues related to the volume or weight of food consumed can interact with or override physiological cues associated with food intake.”9

Energy density is defined as the relationship of calories to the weight of food (i.e., calories per gram). Foods like oils, bacon, butter, cookies, crackers, junk food, fast food, etc., are generally considered “high-energy-dense” foods (i.e., 4 – 9 calories per gram by weight); on the contrary, nearly all fresh vegetables (and fruits) are considered “low-energy-dense” foods (i.e., 0.0 – 1.5 calories per gram, by weight), as they tend to have a high water content and be a very good source of fiber, two important factors reducing energy density. Fiber itself has a relatively low-energy density, providing only about 1.5 – 2.5 calories per gram.

Along those lines, researchers have found that when folks consume low-energy-dense foods, they feel satisfied earlier and those feelings of fullness persist for relatively longer periods of time—despite reductions in calorie intake. In other words, diets rich in low-energy-dense foods like fruits and vegetables allow folks to eat more total food, which leads to greater feelings of satiety, all while reducing calorie intake.10 By definition, that’s eating more (overall food) and less (calories). Bingo!

In one study published in the American Journal of Clinical Nutrition, researchers from the University of Alabama allowed participants to eat as much food as they wanted (think all-you-can-eat buffet) over the course of 5 days, and their menu options alternated from low-energy-dense to high-energy-dense foods. On the low-energy-density diet, the folks ate only about HALF of the calories (1570) that they consumed before feeling full compared with the high-energy-density diet (3000 calories).11 Satiety (i.e., fullness and satisfaction) and food acceptance ratings were not different across days, meaning that they didn’t stop eating because they didn’t like the food.

In another study published in the American Journal of Clinical Nutrition, researchers from the CDC found that men and women (over 7,000 of them) who consumed a diet rich in low-energy-dense foods consumed between 275 – 425 fewer calories per day than did those folks who opted for more high-energy-dense foods; not only that, the men and women eating more low-energy-dense foods consumed upwards of 14 MORE ounces of food per day (that’s almost a pound).10 Not surprisingly, the folks who ate more low-energy-dense foods like vegetables had healthier body weights (i.e., lowest prevalence of obesity).

A number of other studies have confirmed these findings: Diets rich in low-energy-dense foods like vegetables, fruits, broth-based soups, high-fiber foods, foods with high water content, etc., promote satiety (i.e., feelings of fullness and satisfaction), reduce hunger, and decrease overall calorie intake.

What’s more, long-term studies have shown that low-energy-dense diets also promote weight loss. In fact, studies lasting longer than 6 months demonstrate that folks who eat more low-energy-dense foods experience THREE TIMES greater weight loss than people who simply opt to reduce calories.12

In a study published in the American Journal of Clinical Nutrition, researchers from Penn State University found that overweight women who focused on increasing their intake of low-energy-dense foods (i.e., fruits and vegetables) lost nearly 25% more weight over the course of one year compared to women who were instructed to follow a reduced-calorie diet alone. The women who focused on eating more fruits and vegetables ended up consuming MORE food (despite consuming fewer calories) and experienced greater satiety. The researchers concluded, “Reducing dietary energy density, particularly by increasing fruit and vegetable intakes, is an effective strategy for managing body weight while controlling hunger.”13

With all of that in mind, it should be a bit more clear how you can eat less and more at the same time to support your body composition goals by centering much of your food intake around low-energy-dense foods. This is not only an effective strategy for improving appetite control and reducing caloric intake. You see, what these low-energy-dense foods lack in calories more than make up for in their nutrient density, as they are packed with fiber, essential micronutrients, and important phytochemicals that act as potent antioxidants.

Examples of low-energy-dense foods:

  • Nearly all fresh vegetables and fruits
  • Colorful, starchy vegetables and fruits (e.g., bananas, potatoes, squash, yams)
  • Broth-based soups
  • Beans and lentils
  • Dairy (e.g., Greek yogurt, cottage cheese, milk)
  • Minimally-processed whole grains (e.g., quinoa, maize, amaranth, oats, rice, barley, sprouted grains, spelt, etc.)

Another Hunger Buster

Speaking of satiety, the discussion would not be complete without mentioning dietary protein, which is a nutrition all-star for a number of reasons, including its impact on appetite control.

In general, protein-rich foods result in a greater sense of satisfaction than fat- or carbohydrate-rich foods, and when you eat protein-dense meals, they tend to decrease calorie intake in subsequent feedings. In other words, protein-rich foods and protein-dense meals help you feel fuller, longer.14

Not only that, dietary protein exerts a significantly higher “thermic effect” than fats or carbohydrates, and high-protein meals are associated with increased thermogenesis. Simply put, a higher protein intake increases energy expenditure and boosts the metabolism.15

Even more, high-protein diets help build and maintain lean body mass and preserve metabolic rate, both of which are frequently compromised when dieting for fat loss.16 High-protein diets also tend to lead to significantly greater fat loss, and as a result, markedly better improvements in body composition.

As a matter of fact, when researchers from the University of Illinois compared the effects a high-protein diet to a standard reduced-calorie diet, they found that those folks who consumed more protein experienced a 62% greater ratio of fat loss—even though both groups consumed the same number of calories. 17

The researchers concluded, “This study demonstrates that increasing the proportion of protein to carbohydrate in the diet of adult women has positive effects on body composition, blood lipids, glucose homeostasis and satiety during weight loss.”

Despite the benefits on body composition, metabolism, and appetite, most folks don’t consume enough protein, and eating lean protein at each meal—a key habit of highly effective nutrition plans—along with low-energy dense foods can be tricky. That’s why a high-quality protein supplement tends to be foundational for optimizing overall health, body composition, and performance.

Because protein supplements are typically mixed with water or low-calorie liquid (e.g., unsweetened almond milk), they are inherently low-energy-dense options. For instance, the protein supplement recommended above mixed with 8 ounces of unsweetened almond milk has an energy density of about 0.6 calories per gram.

What’s also neat about a protein supplement is that it provides an opportunity to “sneak” in more low-energy-dense vegetables and fruits. For instance, you can add a couple of handfuls of spinach and some berries to make a great-tasting, nutrient-dense, low-energy dense protein smoothie.

As mentioned above, certain forms (e.g., cottage cheese, Greek yogurt, milk) of dairy are low-energy-dense and protein-dense, and a number of studies have demonstrated that dairy consumption may contribute to increases in lean body mass along with losses in body fat (i.e., improved body composition).18–22

Some folks do take issue with dairy, and in many cases, mild discomfort (whether real or perceived) can be alleviated by gradually increasing consumption and/or through use of digestive enzyme supplementation. While most digestive enzyme supplements in this category tend to only supply the lactase enzyme—which is necessary for the proper breakdown of the sugar lactose found in milk—it’s a better idea to consider a full-spectrum product that also includes proteolytic enzymes to help with the digestion of the proteins (e.g., whey, casein) found in milk, as they may also contribute to digestive discomfort.

Note: The majority of lean protein sources (e.g., beef, poultry, seafood, eggs, wild game, etc.) classify as “medium-energy-dense” foods, but they are still exceptional food choices and provide extraordinary nutrient density. As cited above, there are numerous advantages behind consuming protein-rich foods and a high-protein diet beyond the energy density discussion.

Move More, Eat More 2.0

Another interesting application of the “Move more, eat more” concept is what Dr. John Berardi has long advocated and described as G-Flux.23 The concept behind G-Flux, or energy flux, is that there is a multitude of benefits associated with a concomitant increase in both energy expenditure and calorie intake, including:

  • Improvements in body composition
  • Increased metabolic rate
  • Better recovery from and adaptations to exercise
  • Improved health
  • Greater nutrient density and improved micronutrient delivery

In general, when one increases activity (e.g., exercise), s/he burns a certain number of calories. Likewise, any time that you eat, your body expends energy (i.e., thermic effect of feeding) to digest, absorb, and assimilate the nutrients contained in food. With that in mind, there should be a predictable increase in energy expenditure when folks increase both physical activity and food intake.

What’s particularly interesting is that research suggests that these “high energy flux” states result in an unexpected and significant increase in the number of calories burned. In other words, when folks simultaneously increase physical activity and food intake, they tend to show significant increases in resting metabolic rate and burn even more calories than would be expected.24,25 Pretty nifty trick, and even more evidence of the “Move more, eat more” slogan.

What’s also interesting to note is that many folks tend to subconsciously increase non-exercise activity levels when they consume more calories. In other words, researchers have found that some people innately burn off more energy—through fidgeting, maintaining posture, daily activities—in response to overeating in order to preserve leanness and avoid gaining body fat.26 Thus, eating more can actually facilitate moving more, which enhances energy flux and body composition.

Take-Home Points

  • When it comes to fat loss, “Move more, eat less” makes sense, and it’s based on fundamental principles of human physiology. Although many researchers argue that there are other factors in play, an imbalance of calories consumed versus energy expended best describes how body weight changes.27 With that said, this common axiom is overly simplistic, and it doesn’t take into account other important factors (e.g., environment, hedonic compensation) that may influence food intake and eating behaviors.
  • “Move more, eat more” means that you can actually eat a substantially larger volume of food (i.e., low-energy-dense foods), which leads to greater satiety, fewer calories consumed, and greater overall nutrient intake.
  • Especially when starting a fat loss program, begin with the highest possible calorie intake. This leaves the most room for progression along the way. Dramatic reductions in food intake result in significant decreases in energy expenditure (e.g., reduced thermic effect of feeding, decreased cost of physical activity, reduced resting metabolic rate, and metabolic adaptations).28,29
  • Try not to get too caught up in the “numbers game.” While calories in versus calories out may be a rational scientific explanation, it’s virtually impossible to estimate the number of calories that you expend during activity or over the course of the day. Calorie counting can be a futile process, as labels and reporting may lead to estimates with a 30% margin of error. What’s more, without sophisticated equipment, it’s not feasible to accurately assess the number of calories absorbed.
  • When you’re encroaching on a plateau, experiment with the G-Flux concept—simultaneously increase physical activity and food intake. Done progressively, in most cases, folks tend to see rapid improvements in body composition and performance. In the worst cases, they remain at the plateau, and even then, they tend to add some muscle.
  • When you’ve reached your ideal body composition, consider the G-Flux approach as well to help facilitate a higher calorie intake. Once you’re able to maintain a stable weight at the higher energy intake, gradually decrease physical activity.

References:

  1. Hall KD, Heymsfield SB, Kemnitz JW, Klein S, Schoeller DA, Speakman JR. Energy balance and its components: implications for body weight regulation. Am J Clin Nutr. 2012;95(4):989-994. doi:10.3945/ajcn.112.036350.
  2. Wing RR, Hill JO. Successful weight loss maintenance. Annu Rev Nutr. 2001;21:323-341. doi:10.1146/annurev.nutr.21.1.323.
  3. Greenway FL. Physiological adaptations to weight loss and factors favouring weight regain. Int J Obes. 2015;39(8):1188-1196. doi:10.1038/ijo.2015.59.
  4. Berthoud H-R. Metabolic and hedonic drives in the neural control of appetite: who is the boss? Curr Opin Neurobiol. 2011;21(6):888-896. doi:10.1016/j.conb.2011.09.004.
  5. Martínez-González MA, Martínez JA, Hu FB, Gibney MJ, Kearney J. Physical inactivity, sedentary lifestyle and obesity in the European Union. Int J Obes Relat Metab Disord J Int Assoc Study Obes. 1999;23(11):1192-1201.
  6. Pietiläinen KH, Kaprio J, Borg P, et al. Physical inactivity and obesity: a vicious circle. Obes Silver Spring Md. 2008;16(2):409-414. doi:10.1038/oby.2007.72.
  7. Spees CK, Scott JM, Taylor CA. Differences in amounts and types of physical activity by obesity status in US adults. Am J Health Behav. 2012;36(1):56-65.
  8. Holt SH, Miller JC, Petocz P, Farmakalidis E. A satiety index of common foods. Eur J Clin Nutr. 1995;49(9):675-690.
  9. Rolls BJ, Bell EA. Intake of fat and carbohydrate: role of energy density. Eur J Clin Nutr. 1999;53 Suppl 1:S166-S173.
  10. Ledikwe JH, Blanck HM, Kettel Khan L, et al. Dietary energy density is associated with energy intake and weight status in US adults. Am J Clin Nutr. 2006;83(6):1362-1368.
  11. Duncan KH, Bacon JA, Weinsier RL. The effects of high and low energy density diets on satiety, energy intake, and eating time of obese and nonobese subjects. Am J Clin Nutr. 1983;37(5):763-767.
  12. Yao M, Roberts SB. Dietary energy density and weight regulation. Nutr Rev. 2001;59(8 Pt 1):247-258.
  13. Ello-Martin JA, Roe LS, Ledikwe JH, Beach AM, Rolls BJ. Dietary energy density in the treatment of obesity: a year-long trial comparing 2 weight-loss diets. Am J Clin Nutr. 2007;85(6):1465-1477.
  14. Paddon-Jones D, Westman E, Mattes RD, Wolfe RR, Astrup A, Westerterp-Plantenga M. Protein, weight management, and satiety. Am J Clin Nutr. 2008;87(5):1558S – 1561S.
  15. Halton TL, Hu FB. The effects of high protein diets on thermogenesis, satiety and weight loss: a critical review. J Am Coll Nutr. 2004;23(5):373-385.
  16. Soenen S, Martens EAP, Hochstenbach-Waelen A, Lemmens SGT, Westerterp-Plantenga MS. Normal protein intake is required for body weight loss and weight maintenance, and elevated protein intake for additional preservation of resting energy expenditure and fat free mass. J Nutr. 2013;143(5):591-596. doi:10.3945/jn.112.167593.
  17. Layman DK, Boileau RA, Erickson DJ, et al. A reduced ratio of dietary carbohydrate to protein improves body composition and blood lipid profiles during weight loss in adult women. J Nutr. 2003;133(2):411-417.
  18. Josse AR, Atkinson SA, Tarnopolsky MA, Phillips SM. Increased Consumption of Dairy Foods and Protein during Diet- and Exercise-Induced Weight Loss Promotes Fat Mass Loss and Lean Mass Gain in Overweight and Obese Premenopausal Women. J Nutr. 2011;141(9):1626-1634. doi:10.3945/jn.111.141028.
  19. Zemel MB, Richards J, Mathis S, Milstead A, Gebhardt L, Silva E. Dairy augmentation of total and central fat loss in obese subjects. Int J Obes 2005. 2005;29(4):391-397. doi:10.1038/sj.ijo.0802880.
  20. Wilkinson SB, Tarnopolsky MA, Macdonald MJ, Macdonald JR, Armstrong D, Phillips SM. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. Am J Clin Nutr. 2007;85(4):1031-1040.
  21. Hartman JW, Tang JE, Wilkinson SB, et al. Consumption of fat-free fluid milk after resistance exercise promotes greater lean mass accretion than does consumption of soy or carbohydrate in young, novice, male weightlifters. Am J Clin Nutr. 2007;86(2):373-381.
  22. Josse AR, Tang JE, Tarnopolsky MA, Phillips SM. Body composition and strength changes in women with milk and resistance exercise. Med Sci Sports Exerc. 2010;42(6):1122-1130. doi:10.1249/MSS.0b013e3181c854f6.
  23. Andrews R. All About G-Flux. Precis Nutr. http://www.precisionnutrition.com/all-about-g-flux.
  24. Bullough RC, Gillette CA, Harris MA, Melby CL. Interaction of acute changes in exercise energy expenditure and energy intake on resting metabolic rate. Am J Clin Nutr. 1995;61(3):473-481.
  25. Goran MI, Calles-Escandon J, Poehlman ET, O’Connell M, Danforth E. Effects of increased energy intake and/or physical activity on energy expenditure in young healthy men. J Appl Physiol Bethesda Md 1985. 1994;77(1):366-372.
  26. Levine JA. Role of Nonexercise Activity Thermogenesis in Resistance to Fat Gain in Humans. Science. 1999;283(5399):212-214. doi:10.1126/science.283.5399.212.
  27. McAllister EJ, Dhurandhar NV, Keith SW, et al. Ten Putative Contributors to the Obesity Epidemic. Crit Rev Food Sci Nutr. 2009;49(10):868-913. doi:10.1080/10408390903372599.
  28. Saltzman E, Roberts SB. The role of energy expenditure in energy regulation: findings from a decade of research. Nutr Rev. 1995;53(8):209-220.
  29. Trexler ET, Smith-Ryan AE, Norton LE. Metabolic adaptation to weight loss: implications for the athlete. J Int Soc Sports Nutr. 2014;11(1):7. doi:10.1186/1550-2783-11-7.