Top critical review
Complete Overview Of Cherry Picking And Incorrect Information
Reviewed in the United States on July 13, 2020
My wife and I personally practice intermittent fasting, and this book is a very thorough compilation of an overview of its benefits, as well as a vast reference book of sorts to the many ever emerging studies. Gin provides an easy-to read, extensive overview of the science of IF, many practical approaches to follow, a thorough FAQ, and plenty of motivation along the way. For other potential strengths, read the many other glowing reviews.
That said, my issue with Fast Feast Repeat is twofold: it contains an overwhelming amount of cherry picking (even if in favor of a viewpoint I agree with), as well as a patronizing tone. Allow me to explore both.
I was motivated by Gin’s opening call to action. As she says, “...as you read my words, feel free to double-check everything I am saying by going straight to the studies and source material that I reference. I pledge that I am not going to misrepresent any of the scientific material that I present like so many authors do. (This is actually a real problem with many books in the health field. More times than I can count, I have read a claim and then gone to the study referenced by the author, and it’s like we were reading two different papers: the original study doesn’t say what the book author claims it says. I promise not to do that to you.)”
Per Gin’s urging, I did just that. While many studies showed exactly what she said, many did not. Painting herself as an unbiased source while delivering a bias is perhaps one of the most dangerous routes for spreading information, as it can lead to trusted authoritative sources spreading incorrect information.
Gin notes the issues with using rodent studies for IF evidence. This serves to give her credibility, while simultaneously green lighting her use of them. She does not mention the fact that 24 hour fasted studies in rodents are likely the equivalent of much longer fasts in humans. As such, I believe any study should have been noted for if it was conducted in rodents. (Alternatively, she could have only used rodent studies to support IF claims for longer, extended fasts). Second, rodents have the opposite circadian rhythm of humans, which is not noted nor accounted for in Fast Feast Repeat. As such, any study used to testify to IF, if done in a rodent, may or may not apply to the type of daily IF prescribed in the book.
Gin states, "Research shows that IF decreases gherlin (the satiety hormone) and increases leptin (the satiety hormones).” Her referenced studies do not support this, and in fact show the opposite. Her first referenced study ("Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting") says that IF decreases leptin, and provides no commentary on ghrelin, though it does reference another study on it. When we look up that study ("Impact of Reduced Meal Frequency Without Caloric Restriction on Glucose Regulation in Healthy, Normal Weight Middle-Aged Men and Women"), comparing one meal a day to 3 meals a day, it found no difference in leptin, and "no significant effects of meal frequency on plasma levels of ghrelin, adiponectin, resistin or BDNF.” It also noted that " insulin sensitivity was apparently decreased in subjects when consuming 1 meal/d,” and suggests that IF can only improve glucose regulation if it is calorie restricted, which flies in the face of many other claims throughout her book. Her second referenced study notes that IF decreases leptin, with no mention of ghrelin.
Gin does not provide an accurate picture of ketone use in the body. As she states: “Let me explain. When your body uses ketones efficiently, there are fewer ketones being excreted, or released, in your urine or your breath, and you also won’t have as many hanging around in your blood. If you try to measure, it may appear that you are not making many ketones, when in actuality, your body is just becoming really good at using the ketones that you have made.”
This is not entirely correct. When entering the ketogenic state, excess acetoetate may be excreted as urinary ketones, which may taper down with continuation in ketosis. Breath ketones, however, do not tend to taper down, and perhaps most importantly, blood measurements typically increase when getting deeper into ketosis. The fact that your body becomes more “efficient’ at using ketones, does not mean blood measurements will go away (If so, what would you be running on?). On the contrary, blood measurement tend to increase, and breath measurements tend to align with accuracy to blood measurements.
Gin states that “sweet, sour, and umami foods increase saliva secretion (which helps our bodies prepare for digestion and food absorption) while bitter flavors (such as black coffee and plain tea) do not have this effect.” The cited study ("Effects and Mechanisms of Tastants on the Gustatory-Salivary Reflex in Human Minor Salivary Glands”) simply doesn’t show that. Rather, it found that ALL flavors did not increase saliva in low concentrations, but did increase saliva in high concentrations. As it notes, "The present study has shown that each of the five basic taste sensations can induce human [saliva] secretion.” It’s possible she briefly read the abstract, saw that bitter did not stimulate nearby blood flow (which is different than saliva), and applied that to the saliva aspect as well.
Gin uses her false statement bitter saliva claim to support other statements throughout the book, such as why coffee - with its bitter flavor - is ok for the fast, due to not releasing insulin. As noted, this is not what the study found. On top of that, there ARE studies showing coffee releases insulin. ("Coffee consumption is positively related to insulin secretion in the Shanghai High-Risk Diabetic Screen (SHiDS) Study," "Effects of coffee consumption on glucose metabolism: A systematic review of clinical trials,” "Effects of Coffee Consumption on Fasting Blood Glucose and Insulin Concentrations," etc.) While some have found a favorable effect on glucose metabolism, this only further skews Gin’s argument that insulin release is always something to be avoided during the fast. If coffee can release insulin, encourage fat burning, and support autophagy, should it still be ok for the “clean fast”? Gin has black and white parameters for her “clean fast,” and then cherry picks findings to support her preferences.
EARLY VS. LATE NIGHT EATING
Across the board, literature overwhelmingly supports more favorable glycemic responses to early vs late night eating. To address this, Gin cites one study ("Time-Restricted Feeding Improves Glucose Tolerance in Men at Risk for Type 2 Diabetes: A Randomized Crossover Trial"), saying “Scientists found that participants had similar improvements in glycemic response, no matter which time of day they ate.” The study actually found that only an early fasting window lowered mean fasting glucose, and early eating was superior to later eating in improving glycemic responses (though both were better than “normal” eating.) As it says, "There is also a known circadian impact of meal timing, with poorer glucose tolerance at night despite identical meals and equidistant fasting lengths.”
Gin states completely false information from at least one study. In discussing "Postprandial energy expenditure in whole-food and processed-food meals: Implications for daily energy expenditure,” she says "scientists compared two different cheese sandwiches: one that was made from highly processed bread and cheese and another that was made from more “whole” versions. It took almost 47 percent more energy to digest the less processed version of the sandwich, and the metabolic rates of the participants went up as they digested the meal! ” The study actually states that the "The DIT of the PF meal was 46.8% lower than the DIT of the WF meal.” Doing the calculations, this means the “whole" version took around 88% more energy, not 47%. As the study says, “the metabolic processes associated with DIT consumed approximately twice as much energy for the WF meal compared to the PF meal.” While this was likely not an intentional misrepresentation - as reporting the higher number would have been more in her favor - it nevertheless shows she does not always accurately relate the data found in studies.
In discussing exercise, Gin says “Exercise alone is unlikely to result in meaningful or significant weight loss, and studies have backed this up.” This simplistic statement does not account for why this may be the case. Namely: that exercise alone often results in overcompensation of calories, reduced physical activity, or failure to maintain the protocol. If exercise alone is added to one’s lifestyle with no dietary or compensatory physical activity change, it can (and most likely will) result in weight loss. Studies have shown this ("Aerobic exercise alone results in clinically significant weight loss for men and women: Midwest Exercise Trial-2," "Reduction in obesity and related comorbid conditions after diet-induced weight loss or exercise-induced weight loss in men," "Effects of Weight Loss on Lean Mass, Strength, Bone, and Aerobic Capacity,” etc.)
Furthermore, the study Gin quotes actually says that "unless the overall volume of aerobic ET is very high, clinically significant weight loss is unlikely to occur,” that "changes in weight in response to ET without caloric restriction are highly heterogeneous and individual differences can span weight gain to clinically significant weight loss,” and that "although the weight loss from ET programs without caloric restriction are very heterogeneous, based on the present literature patients who engage in a PA program may experience modest weight loss(<2 kg), but no weight loss is possible.” In other words: exercise alone results weight loss across the board: from clinically significant weight loss, to weight gain. The study notes these variances likely involve compliance, overcompensation with eating, or other factors. Basically, if exercise doesn’t result in weight loss, it’s likely because people don’t do it as prescribed - not that it's an ineffective route.
While this may seem like nitpicking, I believe the implications are huge. It is these subtle nuances which lead to the development of dogma. The studies and science surrounding exercise alone for weight loss is conflicting, with a myriad of potential factors. A more appropriate way of phrasing things, would have been as her cited study did: "The literature is clear that caloric restriction is more likely to result in clinically significant weight loss compared to aerobic ET alone.” I believe Gin could have phrased things more accurately if she had said, “fasting is more likely to result in meaningful or significant weight loss than exercise alone." The difference here, is noting that diet may be superior to exercise, rather than falsifying the potential effectiveness of an alternative option. (Because in Gin’s world, it would seem that there is no alternative protocol).
Gin asserts that feeling cold during the fast is (across the board) not due to a decrease in metabolism. She cites that fasting reduces blood flow to extremities. While this may be the case for why hands and feet feel cold, that is not the same as a lowered core body temperature. In fact, her referenced study bears no mention of body temperature. If we research core body temperature and fasting, studies show drops in core body temperature do in fact occur while fasting, the extent of which likely involves genetic individuality. Those with “thrify genotypes” experience a larger decrease in core metabolism, and correlated decreased energy expenditure. In other words, if you feel cold at the core from fasting, your energy expenditure may indeed be reducing.
Furthermore, Gin’s cited study note that "Data from the Baltimore Longitudinal Study of Aging indicate that men with body temperature below the median live longer, which makes it tempting to speculate that a more energy-conserving (thrifty) phenotype can result in increased longevity.” This is in stark contrast to Gin’s next statement: that a lowered body temperature over time is a “bad sign”. For her argument, she cites a 2009 study exploring a correlation between the obese and lowered body rates. Not only has alternative research found the exact opposite ("Human body temperature is inversely correlated with body mass"), but follow-up research since then has questioned the obesity/lower body temperature connection, indicating she didn’t do thorough research of the subject. (2009’s "Adiposity and human regional body temperature," 2011’s "Core body temperature in obesity," 2012’s "24‐h Core Temperature in Obese and Lean Men and Women.") It may be that low body temperature and obesity is a case of correlation not causation. As a 2011 study notes, "Little has been published regarding the relationship of BMI to core body temperature. Some have hypothesized that obesity is associated with lower body temperature, consistent with a lower resting metabolic rate. Of the five identified studies examining temperature and body weight, three (encompassing a total of 334 participants) found lower values while two, with a total of 866 individuals, reported higher body temperatures associated with increased BMI. Our data gathered in a far larger population than the sum of all the prior analyses clearly indicate that obesity is associated with higher body temperature in an almost quantitative manner. It is possible that the association is based on the function of adipose tissue as an inflammatory organ with adipose mass related to total inflammatory mediator production."
Furthermore, if a person loses weight on IF, and is at a lower body weight, it is hard to extrapolate these finding surrounding body temperature to that arguably more healthy hormonal state.
I believe intermittent fasting is profound, and even if Gin is correct in her presented ideas, this does not grant the right to cherry pick studies and misinterpret them, in order to create one “accepted” form of IF. What if you question Gin’s clean fast, or even experience weight loss without following Gin’s specific "fasting clean?” protocol. Questioning should ALWAYS be encouraged, but Gin reprimands such questions by labeling the questioner as a “rebel,” and asserting he or she is actually not achieving the hormonal and metabolic benefits from the fast. (She tends to maintain a very patronizing tone throughout the entire book, treating all readers like inept schoolchildren who can’t understand anything without her guidance. In fact, I almost stopped reading it - it was that bad.) Her “rebel” retort is extremely narrow-sighted, in which a “teacher” brands questioning “students” with labels. To address that specific question (dare you ask it!), weight loss and calorie restriction are linked to numerous health benefits, and some even argue the majority if not all of IFs benefits are due to such. If a person does indeed lose weight with IF while having cream in their coffee - as many have - this does not negate the fact that they are likely experiencing hormonal benefits.
I am not writing this post to argue against IF. I believe intermittent fasting is profound. I am writing this to question Gin as an “unbiased” source of information. Last time I checked, a primary goal of science was testing and questioning hypotheses: discouraging such is a dismal sign for progress towards truth. When reading Fast Feast Repeat, Gin makes it clear it is best to do exactly as she says, in order to be a teacher’s pet. (In her words, “you keep our classrooms running smoothly.”) If you question her narrative (which I have already shown contains false information), you are automatically branded a rebel… even if you were right.
Well Gin, I did my homework. You said to "go to the source just to make sure or to gain a deeper understanding for yourself.” When I did that, I found out you are not always correctly “teaching us."