Ketogenic Diets: What You Need to Know

Ketogenic diets (Keto) have dominated the "popular” diet scene for the past two years, with no close contenders. Prior to Keto’s steady upsurge the popular-diet crown had long rested on gluten-free, although Paleo almost matched it for a few years.

Looking further back (except for the ‘low-fat’ 1990’s) a variety of low-carbohydrate/high-protein diets (i.e., Atkin’s, The Zone, South Beach, etc.) have generally topped the public’s interest. One should at least wonder, if any of these diets really worked then why do they lose popularity only to be replaced by another? 

So Considering Keto...

First of all, what is ketosis? Your brain and central nervous system function on only two fuels, glucose or ketones. Normally ketones would only come into play if you were literally starving—when carbohydrate intake is too low to provide enough fuel in the form of glucose. At that point your body shifts to converting the fuel it always has an abundance of (body fat) to ketones. Similarly, by limiting carbohydrate intake to just around 5% of energy intake (~20 to 50 grams per day) ketogenic diets trigger your body to shift into ketosis.

What is the theory behind ketogenic weight loss diets? Advocates of Keto assert that it's a path to easy weight loss due to to the following: First, because your body is utilizing fat as its main energy source that weight loss is faster. Second is the assertion that Keto has a “metabolic advantage” in the form of a bumped up metabolic rate. And the final assertion is better appetite regulation (you simply won’t be hungry) which makes lower calorie intake easier.

So how do these claims hold up? Ketogenic diets do shift energy metabolism to a predominantly fat-burning mode, but does this speed up weight loss? No, it does not. And actually there is no theoretical reason why it would speed weight loss because it does nothing that changes overall energy balance. We’d have to reconsider the laws of thermodynamics for that to be the case. Let’s look at two key studies.

The following two studies were both tightly controlled metabolic ward studies where every gram of energy intake and output (including urine and feces) were accounted for along with changes in body weight and composition (fat mass, lean body mass and water).

First is a classic nitrogen-balance study[1] comparing an 800-calorie ketogenic diet with an 800-calorie balanced diet both diets led to the same amount of body-fat loss and body-weight loss over the 50-day study. The ketogenic diet however, gave the appearance of more rapid weight loss in the beginning due to extra water losses: 61% versus 37% of early scale loss was water on the ketogenic and balanced diets respectively. Both diets contained the same amount of protein (50-grams) so they differed only in fat and carbohydrate.

More recently, an abbreviated version of this type of study was done by the National Institutes of Health comparing high-fat and high-carbohydrate diets.[2] Over the 6-day metabolic ward study the high-fat diet led to less fat loss than the high-carbohydrate diet (245±21-grams versus 463±37-grams respectively). Why the big difference, and why more fat loss on the high-carbohydrate diet? Because in the early stages of carbohydrate restriction the body breaks down and oxidizes protein (muscle) to maintain blood glucose levels. So in the short-term, the high-fat diet leads to greater muscle, glycogen, and water losses (creating the illusion of faster weight loss) than an equal-calorie high-carbohydrate diet. This well-known protein-sparing effect of carbohydrate is why medically-supervised very-low-calorie (liquid) diets are relatively high-carbohydrate/low-fat formulations.

The first two assertions of Keto advocates (an advantage to a higher rate of fat-burning and a general metabolic advantage) are shown to be false in these meticulous studies, and there are no competing metabolic ward studies that show otherwise.

Scores of studies over the past 40- to 50-years have compared various diets, and report a variety of results (mainly because they are too short or poorly designed, and sometimes outright bias). What is consistent however, is that whenever calories are held constant between two different diets, there is never a significant difference in weight loss. At this point it is exceedingly clear that any diet that creates an energy deficit leads to weight loss.[3]^,[4]

The Real world: People obviously don’t live in metabolic wards. In so-called "free-living" conditions, high protein diets consistently show greater weight loss at three months, and at six months. At one year however, the differences are no longer statistically significant. Why? First, both Keto and high-protein diets lead to excess loss of body water (for the first week or so). More importantly for the long term, the improved satiety effects of higher protein intakes lead to lower energy intake and therefor greater weight loss than a balanced or low-fat diet. Keto diets are only moderate in protein, but ketones have a strong satiety effect of their own[5]^,[6] which will certainly enhance the likelihood of maintaining a lowered energy intake. On the other hand, sticking to a ketogenic diet is especially challenging due to the severe level of carbohydrate restriction (5% of intake versus 40- to 55% of typical diet patterns).

The Bottom Line: of the three proposed advantages of keto diets only reduced appetite is a supportable claim. Given the laws of thermodynamics there is no theoretical reason why changes in fuel oxidation (increased fat-burning) would enhance weight loss. The same goes for the notion of “metabolic advantage” (which also fails to materialize in calorie-controlled studies).

Other important considerations: the long-term health effects of Keto remain to be determined.^[7] Specific areas of concern include a negative impact on the microbiome (resulting in leaky gut, and autoimmune response and systemic inflammation^[8]), reduced micronutrient intakes, enhanced loss of lean body mass, increased homocysteine levels, increased LDL-cholesterol and reduced bone mineral density via excess calcium excretion.[9]

Final thoughts: If you want success with your weight and health the tried and true approach is to learn how to eat in a healthy way and in healthy amounts. My best advise is to start where you are at, and look for "easy changes" to improve the quality of your diet. Forget "going-on-a-diet," instead approach it as a lifestyle change. It would also help a lot to understand more about how your body works. Here are some links that can help you get started:

• The Game of Weight Loss has Rules
• 5 Things You Need to Know about Protein for Healthy Weight Loss
• Manage Yourself to Success!

All the Best!
-Dorene

PS--you might also be interested in: Can You Spot a Sham Weight Loss Diet? 

References:

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[1] Yang and Van Itallie: Composition of Weight Lost during Short-Term Weight Reduction: Metabolic responses of obese subjects to starvation and low-calorie ketogenic and nonketogenic diets. J Clin Invest 1976;58:722-730.

[2] Hall K, et al.: Calorie for Calorie, Dietary Fat Restriction Results in More Body Fat Loss than Carbohydrate Restriction in People with Obesity. Cell Metabolism 2015;22:427-436.

[3] Obert J, et al.: Popular Weight Loss Strategies: a Review of Four Weight Loss Techniques. Curr Gastroenterol Rep 2017;19(12):61.

[4] Atallah R, et al.: Long-term effects of 4 popular diets on weight loss and cardiovascular risk factors: a systematic review of randomized controlled trials. 2014;7(6):815-827.

[5] Gibson aa, et al.: Do ketogenic diets really suppress appetite? A systematic review and meta-analysis. Obes Reviews 2015;16:64-76.

[6] Johnstone AM, et al.: Effects of a high-protein ketogenic diet on hunger, appetite, and weight loss in obese men feeding ad libitum. Am J Clin Nutr 2008;87(1):44-45.

[7] Hamdy O, et al.: Fat Versus Carbohydrate-Based Energy-Restricted Diets for Weight Loss in Patients with Type 2 Diabetes. Curr Diab Rep 2018;1812(128).

[8] Tambo A, et al.: The Microbial Hypothesis-Contributions of Adenovirus and Metabolic Endotoxaemia to the Pathogenesis of Obesity. Intl J Chron Disease 2016;7030795.

[9] Adam-Perrot A, et al.: Low-carbohydrate diets: nutritional and physiological aspects. Obes Rev 2006;7(1):49-58.

Claim #3: Eating More Frequently Boosts Your Metabolism

This is entry #3 in a 9-part series on Metabolic Myths.

Metabolism-boosting hype generally has a grain of truth behind it that has been way overblown. In other cases, long disproved theories continue to be touted because they are super effective as click-bait (or selling books). You rarely see any actual numbers -- how many calories per day will this raise my resting metabolic rate? -- attached to claims. That’s because for the most part the actual increase (if any) in resting metabolic rate (or other components of your daily total energy expenditure), is too small to be of any practical significance.

Metabolism mythology has a life of its own though as it gets regurgitated and reposted throughout the internet and fad-diet books (and unfortunately even by many otherwise reputable sources).

Review "Metabolism" here: Metabolic Rate

My last topics were muscle and breakfast, today's topic is eating-more-frequently:

CLAIM: Eating More Frequently will Boost Your Metabolism

The notion that eating more often was conducive to lower body weights got started in the 1960s when researchers noticed higher body weights were correlated with fewer eating occasions in epidemiological studies. However, the self-reported energy intakes in those kinds of studies was long ago shown to be flawed and unreliable. Since then randomized controlled trials have shown what would be expected, that total daily energy intake increases along with the number of eating occasions per day—not the opposite.[i]

Despite this, dieting advice encouraging a more frequent eating pattern of smaller meals continues to be propagated. One popular claim is that this pattern raises for metabolism.

Despite the fact that digesting and assimilating what you eat DOES burn calories, it does NOT affect your underlying metabolic rate. By definition the thermic effect of food (TEF) is the measured energy expenditure above Resting Metabolic Rate (RMR) in response to eating.

TEF averages 10% of calories consumed for “mixed” meals (combinations of protein, carbohydrate and fat). The number one determinate of TEF is calories. For a given number of calories TEF remains the same whether those calories are divided into 3-meals, 6-meals, or eaten all at once.[ii]

A related theory behind advice to eat more often, is that eating more often would decrease hunger and increase satiety so that people would avoid overeating “later.”

Studies investigating this theory keep total calorie intake the same, and lean toward showing that larger-meals are more satisfying than smaller meals.[iii] With a full-sized meal you have the physical sense that you've eaten “enough,” versus a snack-size-meal that doesn't have enough volume or energy for your body to register physical or psychological satisfaction.[iv]

Another interesting thread to this area of research is the effect of irregular meal patterns (random snacking) on blood glucose, insulin sensitivity and appetite related hormones. Our bodies aclimtize to, and function best, with a regular meal pattern.[v][vi]

It's important also to point out that when you reduce your energy intake to promote weight loss, your remaining calorie allotment may not be enough to create filling meals and snacks. On the other hand, when eating to maintain your weight your calorie allotment stretches further providing more flexibility.

If you get hungry between meals, the first thing you need to do is evaluate exactly what you’re eating that fails to keep hunger-at-bay until the next meal? The problem is most likely the combined issues of: a) too much sugar and/or refined carbohydrates, and b) not enough protein. Shoot for 25- to 30-grams of protein at each of your main meals, and choose more nutrient-dense whole foods. Then (assuming each meal also provides adequate calories) you shouldn’t feel hunger before it’s “time-to-eat” again.

It's perfectly fine to snack between meals if you prefer that pattern (and can do it within your calorie allowance). There's no benefit, however, to changing to a snacking pattern if you're not a snacker. Whether your goal is weight loss or not the majority of your snacks should ideally be healthy choices that help you meet your nutrient requirements for the day.

The bottom line: Suggestions that eating smaller more frequent meals will increase your metabolsim are simply false. Dividing your calories between more meals does NOTHING to increase your underlying (or total) metabolism. That's good news, you can stick to whatever pattern that you've found works best for you be it snacky or not.

All the best,
-Dorene

References:

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[i] The impact of daily meal pattern on energy Balance. Bellisle, F. Scan J Nutr 2004;38(3):114-118.

[ii] The Energy Content and Composition of Meals Consumed after an Overnight Fast and Their Effects on Diet Induced Thermogenesis: A Systematic Review, Meta-Analyses and Meta-Regressions. Quatela, et al. Nutrients 2016;8(11)670.

[iii] The Effect of Eating Frequency on Appetite Control and Food Intake: Brief Synopsis of Controlled Feeding Studies. Leidy and Campbell. J Nutr 2011;141:154s-157s.

[iv] Evidence for Efficacy and Effectiveness of Changes in Eating Frequency for Body Weight Management. Kant, AK. Adv Nutr 2014;(5):822-828.

[v] Association between eating frequency, weight, and health. Palmer, et al. Nutr Reviews 2009;67(7):379-390.

[vi] When to eat and how often? Parks and McCrory. Am J Clin Nutr. 2005;81:3-4.

CLAIM #1: Breakfast Boosts Your Metabolism... (#1 of 9 "Boost Your Metabolism" Claims that are Actually False)

Metabolism-boosting hype generally has a grain of truth behind it that has been way overblown. In other cases, long disproved theories continue to be touted because they are super effective as click-bait (or selling books). You rarely see any actual numbers -- how many calories per day will this raise my resting metabolic rate? -- attached to claims. That’s because for the most part the actual increase in resting metabolic rate (or other components of your daily total energy expenditure), is too small to be of any practical significance.

Metabolism mythology has a life of its own though as it gets regurgitated and reposted throughout the internet and fad-diet books (and unfortunately even by many otherwise reputable sources).

Each of the following false and misleading "Boost Your Metabolism" topics will be discussed in a separate blog over the next couple weeks (not necessarily in this order): Breakfast, Build Muscle, Meal Frequency, Water, Cheat Meals, EPOC, Hot Peppers, MCTs, and Eating after 7pm.

Myth #1: Breakfast boosts your metabolism.

Claims and advice that eating breakfast in some way promotes weight management continue to be doled out despite a lack of evidential support.[i] This problem is so pervasive that it was the topic of a 2013 scientific paper (by highly respected researchers from University of Alabama at Birmingham's NIH-funded Nutrition Obesity Research Center) basically admonishing the scientific community for biased research, and calling on it to do better.[ii]

Some of the false claims regarding breakfast:

CLAIM: Your metabolism will be higher all day if you start with breakfast

The FACTs: the metabolic response to eating breakfast is not different than that to eating food at any time later in the day.[iii] Digesting and assimilating what you eat is called the thermic effect of food (TEF), and by definition TEF is measured as the energy expenditure above resting metabolic rate in response to eating.[iv] [v]

CLAIM: Skipping breakfast leads to overeating later in the day.

The FACTs:  When breakfast is omitted from the daily meal pattern (skipped) calorie intake at the end of the day is generally lower. In other words, the calories missed at breakfast are not completely offset by eating more at lunch or dinner. So at the end of the day an energy deficit remains.

CLAIM: Skipping breakfast makes you hungry.

The FACTs: The effect of breakfast on satiety is transient and not more advantageous than the next meal of the day provides independent of breakfast.[iv]  Note however, that habitual breakfast-eaters and habitual breakfast-skippers respond differently. That's because your body adjusts to the pattern you usually follow so that it "expects," that pattern. So if you usually eat breakfast, and you try skipping it you’re going to be extra hungry for lunch. On the other hand, breakfast skippers aren’t hungry for breakfast to begin with, and eating breakfast is like a curve ball disrupting their system in a different way (which may be why some people claim that eating breakfast makes them more hungry).

Evidence (from well done randomized controlled trials) does seem to show:

• That breakfast eaters may have higher morning physical activity levels (via less sitting/more moving around) compared to breakfast skippers.[vi]
• People who regularly eat breakfast tend not to be night eaters, so they are hungry when they get up.
• Habitual breakfast eaters also tend to be non-smokers, consume less fat and alcohol but more fiber and micronutrients, and are more physically active.[vii]

Clearly, trying to attribute differences in BMI between breakfast eaters, or skippers, is not a straightforward endeavor.

It is important to note that for diabetics eating breakfast results in lower insulin and blood glucose levels for the rest of the day. So, it is very important that diabetics eat breakfast.

For everybody else, you can stick with what works for you because eating breakfast does NOT increase your (resting) metabolism, improve appetite regulation, or reduce overall energy intake. TEF from breakfast is no different, and provides no advantage over, the TEF from any other meal.

The problem with boost-your-metabolism myths is that they distract you from focusing on what actually works, and propagate the notion that there are simple tricks or magical methods that promote weight loss. The best advice remains to be: eat a healthy diet, but not too much, and make activity a part of your day.

All the best!
-Dorene

References:

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[i] Meal skipping and variables related to energy balance in adults: a brief review, with emphasis on the breakfast meal. McCrory, MA. Physiol Behav 2014;134:51-54.

[ii] Belief beyond the evidence: using the proposed effect of breakfast on obesity to show 2 practices that distort scientific evidence. Brown, et al. Am J Clin Nutr 2013;98:1298-1308.

[iii] The Energy Content and Composition of Meals Consumed after an Overnight Fast and Their Effects on Diet Induced Thermogenesis: A Systematic Review, Meta-Analyses and Meta-Regressions. Quatela, et al. Nutrients 2016;8(11)670.

[iv] The effect of breakfast on appetite regulation, energy balance and exercise performance. Clayton and Lewis. Proc Nutr Soc 2016;75(3):319-327.

[v] Effect of breakfast skipping on diurnal variation of energy metabolism and blood glucose. Kobayashi, et al. Obes Res Clin Prac 2014;8(3):e201-98.

[vii] The effectiveness of breakfast recommendations on weight loss: a randomized controlled trial. Dhurandhar et al. Am J Clin Nutr 2014;100:507–13.

[viii] The causal role of breakfast in energy balance and health: a randomized controlled trial in lean adults. Betts, et al. Am J Clin Nutr 2014;100:539-547.

Does Protein Really Curb Your Appetite?

It's hard not to get misled by misinformation, or hype, when you're searching for reliable information on weight management. The daily rush to publish makes even seemingly reliable sources vulnerable to "getting it wrong"—because it takes time to do enough research to make sure you've got it right.

Nutrition Action didn't 'get it right' with their recent post on protein and appetite: Does Protein Really Curb Your Appetite?

After more than two decades specializing in weight management I have 52 papers tagged under "appetite regulation" in my research database. Appetite regulation is a fascinating and important topic within weight management. I covered it in my 6-hour Advanced Training in Weight Management CE workshop back in 2003 and 2004, and since then have only seen one other seminar on macronutrients and appetite regulation cross my desk. I know the key papers off the top of my head, and I know that the fact that protein has a higher satiety value is not even a question among researchers who are experts in that area.

That said, there are several important caveats...

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Successful Weight Managers Instinctively do This...

We’ve lost track of a structure around eating that had existed for generations. Your grandparents will confirm that until recently a simple structure to our eating activities was followed—and no one questioned or thought about it much.

We ate breakfast and dinner at home, and a lunch was packed to take to work. Meals were large enough that they provided the calories needed to fuel us until the next meal, without needing a snack. Snacking wasn’t the norm, and the vast majority of body weights were in the healthy range. An overweight child was unusual.

Click to read more ...