![]() T3 thyroid hormone levels decreased on all of these severely calorie restricted diets. However, when PUFA was high (50P/10C and 70P/10C) the decrease in T3 was much. Low salt diets are not healthy as research published in peer reviewed medical journals proves. A FREE diet plan guide. Find your ideal daily calorie, protein, fat and carb intake for your goal along with a list of the best food sources for each.
Evidence that supports the prescription of low- carbohydrate high- fat diets: a narrative review. Introduction. Imagine a obese (BMI=3. IR), including hyperinsulinaemia and impaired glucose tolerance together with atherogenic dyslipidaemia (AD) (triglyceride (TG)=3. L (8. 8 mmol/L), HDL- cholesterol (HDL- C)=4. L (1. 1 mmol/L), LDL- cholesterol (LDL- C)=1. L (5. 0. 5 mmol/L)) who enters her family physician's office. Frustrated with her poor health and progressive weight gain, on the advice of a friend, she has decided to begin a low- carbohydrate high- fat (LCHF) Atkins- type diet. How should her physician respond? What evidence does the physician require to make an informed decision? LCHF diets have polarised the opinions of medical caregivers, especially since the publication of Dr Atkins' Diet Revolution in 1. Some believe that these diets effectively treat type 2 diabetes mellitus (T2. DM), obesity and metabolic syndrome. ![]() ![]() Others consider them to be simply a fad. LFHC) diets to reduce the risk of cardiovascular disease. Faced with such conflicting opinions, the clinician may be unsure how to advise this or other similar patients. Here, we provide an updated narrative review of the large body of published evidence describing the physiological effects, efficacy and safety of LCHF diets for the management, especially of this type of patient characterised by IR and AD. A number of systematic reviews have compared the effects of LCHF diets, traditional LFHC diets and other dietary strategies. Collectively, they establish that, for weight loss, LCHF diets are just as effective, if not more so, than LFHC diets. They also highlight a number of significant changes to cardiovascular risk factors in participants adhering to LCHF diets. The strength of these reviews is their systematic research strategy and meta- analysis of data to answer specific research questions. However, this strength limits their relevance to their defined question, not allowing a broader overview of the evidence for metabolic, physiological and other effects of LCHF diets. The aim of this review is not to argue whether LCHF diets are superior to other dietary strategies for any specific health outcome. Rather, we synthesise the evidence for the effects of LCHF diets on weight loss, glycaemic control, modification of cardiovascular risk factors as well as non- alcoholic fatty liver disease (NAFLD) and its associated AD. Further, we address common concerns sometimes presented as reasons why LCHF diets should not be prescribed to any patient. Through this process, we hope to provide clinicians with additional evidence to inform their clinical decision- making, better to understand the potential benefits of these eating plans for at least some patients. Definitions. Though definitions of LCHF diets differ, the following three- tiered definition will be used in this paper. Moderate carbohydrate diet (2. LCHF diet (< 2. CHO/day)Very LCHF (ketogenic) diet (2. CHO/day or < 1. Reduced carbohydrate diets are those that have carbohydrate intakes below the Dietary Guidelines for Americans (DGA) recommendations (of 4. However, we define LCHF diets as those that restrict carbohydrate intake to 1. Very LCHF (ketogenic) diets may induce ketosis in some people. Though individual responses vary, ketosis usually occurs in people who restrict their carbohydrate intake to below 2. Since the carbohydrate content of the diet is significantly reduced, the relative proportion of energy derived from protein and fat will increase. In practice, however, LCHF diets typically produce a reduction in hunger,1. LCHF diet, sometimes significantly. Therefore, even though the relative contribution of fat to dietary energy intake may increase, the absolute fat intake may not. As a result, the term . Hence, the term low- carbohydrate healthy fat is probably more appropriate. What foods are prescribed on the LCHF diet. LCHF diets are defined by what is . Although the details may vary depending on the specific type of LCHF diets (Atkins, Banting, Paleo, South Beach, etc), in each of these examples, there is a consistent focus on eating unprocessed food, consisting primarily of cruciferous and green leafy vegetables, raw nuts and seeds, eggs, fish, unprocessed animal meats, dairy products and natural plant oils and fats from avocados, coconuts and olives. LCHF diets, even if ketogenic, are not . Rather, all encourage a high intake of green leafy vegetables, cruciferous vegetables and other non- starchy vegetables with moderate intakes of berries. Table 1 provides a list of foods recommended on a . LCHF eating plans promote meals such as omelettes, salads and animal protein such as steak, salmon or chicken with vegetables. Table 1. Four decades later, numerous randomised clinical trials (RCTs) and systematic reviews now allow a critical evaluation of the safety and efficacy of LCHF diets for weight reduction. This information was not available to either Osler or Atkins, making a review of this new evidence particularly opportune now. Repeatedly, LCHF diets have performed as well or better than LFHC diets for weight loss in overweight or obese adults. Bazzano et al's. 23 recent 1- year trial randomised 1. T2. DM or cardiovascular disease to an ad libitum LFHC (< 3. LCHF (< 4. 0 g carbohydrates/day) diet. After 1. 2 months, the LCHF diet group had lost significantly (p=0. This equivalent or superior performance of LCHF diets over LFHC diets for weight loss has also been established in randomised trials in adolescents,2. T2. DM. A recent reanalysis (. In a 2. 4- week trial of 8. T2. DM, Westman et al. LCHF diet produced significantly greater weight loss than an energy- restricted (5. RMR), low glycaemic (GI) diet (. The ketogenic LCHF diet also significantly increased blood HDL- C concentrations and reduced blood Hb. A1c values. Additionally, more patients on the LCHF diet were able to reduce or cease their use of diabetic medications. The 1- year A to Z study. Atkins (< 2. 0 g carbohydrates/day induction, < 5. Zone (4. 0% carbohydrate, 3. Ornish (< 1. 0% fat, ad libitum) or LEARN (5. After 1. 2 months, the mean weight loss in the LCHF Atkins group was . Further, blood HDL- C and TG concentrations were significantly improved in the Atkins group compared with all other diet groups, at least initially. Shai et al. 38 randomised 3. Mediterranean diet (MED), energy- restricted LFHC diet or an ad libitum LCHF diet. The most significant weight loss occurred in the LCHF group at 6 months, even though this was the only diet eaten ad libitum—that is, it was not energy- restricted. At the end of the 2. Weight loss on the LCHF diet is greatest early in these trials when participants comply most rigorously to the carbohydrate restrictions, as also occurred at 6 months in the A to Z trial. Subsequent weight gain occurs as participants begin to ingest more carbohydrates daily, so- called . Thus, weight regain is not necessarily the fault of the LCHF diet; rather it is the consequence of its discontinuation. This applies to all dietary interventions, where weight regain occurs with decreased adherence. Conversely, motivated free- living individuals who maintain diet adherence, sometimes to address serious personal medical conditions, self- report weight losses an order of magnitude greater than the rather modest weight losses measured in clinical trials. LCHF diets are no exception, where some have reported effortless weight losses of greater than . However, LCHF diets clearly perform at least as well as do any other dietary approach, even in trials in which energy intake on the LCHF diet is unrestricted (ad libitum). Mechanisms for successful weight loss on the LCHF eating plan. Two main mechanisms have been proposed to explain how LCHF diets produce weight loss, despite an increased consumption of energy- dense . However, in doing so, they excluded trials that demonstrate the advantage of LCHF diets in producing greater satiety and a subsequently reduced energy intake. Indeed, this was the unique biological advantage that Banting,2. Ebstein. 41 and Atkins. LCHF diet on the basis of their clinical observations. Although the original study did not find any differences in weight loss between the different diets, a reanalysis. As an illustration, table 2 lists a collection of studies which show that participants on LCHF diets given unrestricted access to eating foods ad libitum do not necessarily consume more calories than participants assigned to LFHC diets, even when the latter are required consciously to . Regardless of the exact mechanism, it is notable that LCHF diets can achieve an energy deficit and subsequent weight loss with little hunger and without conscious energy restriction, as originally noted by Stock and Yudkin. Postulated . For example, some trials have shown greater weight loss for LCHF diets, despite higher energy intakes than prescribed LFHC diets. Similarly, although some trials find no differences,4. LCHF diets. 3. 3,3. Meta- analyses report similarly variable outcomes. Although contentious, it has been suggested that LCHF diets may provide a metabolic . This metabolic advantage could be attributed to a number of mechanisms, including: (1) increased thermogenic effects of protein intake, (2) greater protein turnover for gluconeogenesis and (3) loss of energy through excretion of ketones in sweat or urine. LCHF diets increase reliance on fat oxidation for energy production, especially during exercise,5. This state of increased lipolysis with reduced lipogenesis contributes to a metabolic milieu theoretically favouring fat loss. This effect is dependent on reduced blood insulin concentrations, uniquely produced by the LCHF diet. However, this remains a contentious idea, with recent metabolic ward evidence suggesting that, at least in the short term (5 days), there is not a preferential fat- loss effect of LCHF diets. LCHF diets in the management of T2. Low Carb High Fat Diets and the Thyroid - Perfect Health Diet. Last year we ran a series on “Zero- Carb Dangers,” which are health problems that can appear if carb intake – or carb+protein intake, since protein can to some degree make up for a deficit of glucose – are too low. Anthony Colpo has recently argued that hypothyroidism should be added to the list of potential zero- carb dangers; and that low- carb high- fat diets in general might create a risk of hypothyroidism. Similar arguments have been made by Matt Stone and others. Our resident thyroid expert, Mario Renato Iwakura, decided to look more deeply into the matter. What does the literature say? There have been anedoctal reports on low carb forums about people becoming hypothyroid after following a low carb, high fat diet. Anthony Colpo recently wrote a blog post about carbohydrate, fat and protein intake and their effects on thyroid hormone levels, concluding that a high fat or high protein diet is detrimental and that a high carbohydrate diet is good for the thyroid . There is no evidence that a diet, such as the Perfect Health Diet, that is high in saturated and monounsaturated fat, low in PUFA, and provides sufficient, moderate levels of protein and carbohydrate, has any detrimental effect on the thyroid. On the contrary, I believe that such a diet is optimal for thyroid health. What Has Been Tested: High PUFA Diets. Colpo’s post is extensive and covered most, but not all, relevant studies published to date about the subject. Many of those studies have problems like short duration or calorie restriction. But in almost all, with the exception of one study by Jeff Volek and collaborators . An example is the Vermont long term study . The excess fat in these diets averaged 8. So, this diet’s fat was probably 1. Or in Ullrich et al 1. All diets were in liquid form, and fat was predominantly PUFA. The composition of the four diets was: 5. P/1. 0C5. 0P/7. 6C7. P/1. 0C7. 0P/8. 6CEnergy (kcal)5. Protein (% cal)3. Fat (% cal)5. 7. 8. Carb (% cal)6. 7. T3 Day 0. 2. 0. 2. T3 Day 2. 81. 1. 1. Variation- 4. 5%- 2. T3 thyroid hormone levels decreased on all of these severely calorie restricted diets. However, when PUFA was high (5. P/1. 0C and 7. 0P/1. C) the decrease in T3 was much larger than when PUFA was low (5. P/7. 6C and 7. 0P/8. C). In a 1. 99. 2 paper, Vasquez et al compared two very low calorie diets (6. The fat sources were soybean oil and refined and stabilized vegetable oils. Ketogenic. Nonketogenic. Protein. 35%3. 4%Fat. Carbs. 9%5. 1%T3 Day 0. T3 Day 2. 80. 8. 1. Variation- 4. 3%- 1. The various studies cited by Colpo also show decreases in T3 levels in diets high in PUFA. In Ullrich et al 1. Thyroxine (T4) and reverse T3 (r. T3) did not change significantly. Thyroid- stimulating hormone (TSH) declined equally after both diets”In the Vermont study . When subjects on the low- carb diet began eating the higher- carb mixed weight gain diet, their T3 levels rose. T3 levels among those who went from the high- carb maintenance diet to the mixed diet remained unchanged. In contrast to T3, serum concentrations of T4 were unchanged by overeating or changes in dietary composition.” . Neither do we have studies showing what happen to T3 levels after a high saturated/monosaturated fat diet is eaten. We will have to rely on indirect evidence. Indirect Evidence: Calories Required to Maintain Weight. There is a connection between thyroid activity and obesity. Reduced thyroid activity reduces energy expenditure (“calories out”) and promotes weight gain; normal thyroid function tends to promote normal weight. So we can use the vast number of obesity studies as indirect evidence for the effects of different types of diet on the thyroid. Anthony emphasized this relationship in his post, noting findings of the Vermont study on overfeeding: “Again, that both groups gained weight should come as no surprise. However, the group overfed the mixed diet required more calories (2,6. Baseline differences in metabolism between the two groups were ruled out, as there was no difference in total calories required to maintain initial lean weights.”So the high- PUFA diet promoted weight gain: it caused excess weight to be retained at a lower calorie intake. This is consistent with reduced thyroid activity. Is this effect due to a high- fat diet generally, or to high- PUFA diets only? Some insight into this question may be found in a blog post by Stephan Guyenet . Rats fed isocaloric diets in which the fat source was varied among three groups – a beef tallow group (primarily saturated fat, 3% PUFA), an olive oil group (primarily unsaturated, 1. PUFA), and a safflower oil group (7. PUFA) – had highly variable weight gains. The olive oil group gained 7. Here is the data, expressed in terms of the percentage of baseline calorie intake that the men had to eat to maintain their weight: The high- fat diet consisted largely of butter and cream; the high- carbohydrate diet of extra sugar. When eating the butter and cream, subjects had to eat more calories to maintain weight than when eating the sugary diet – 2. Every subject had to increase calories when eating high- fat. This suggests higher thyroid hormone levels on the high- saturated fat diet than on a high- carb diet. The Volek Study. Anthony cited a study by Jeff Volek and others . There was a significant increase in total T4 (+1. T3 nor r. T3. They instead tested T3 uptake, an indirect measure of thyroxine binding globulin (TBG) in the blood, which tells us little of any real value about changes in actual thyroid hormone levels. The researchers also measured IGF- 1, glucagon, total and free testosterone, sex hormone- binding globulin (SHBG), insulin- like growth factor- I (IGF- I), and cortisol. The only significant change noted was a reduction in insulin following the low- carbohydrate diet. The Volek study is very interesting because it was not calorie restricted (only carbohydrate was restricted) and was done in normal- weight man. The amount of polyunsaturated fat increased a little (from 6 to 1. Although he did not directly measured T3 nor r. T3 we have indirect evidence that they were not impaired. One very well known fact is that hypothyroid patients, even when taking T4 hormones, usually struggle to lose fat. This occurs because, when thyroid hormones are low, especially when T3 (triidothyronine) is low . If the LCHF diet was impairing the thyroid these healthy normal weight men, who had been advised to eat enough calories to maintain their weight during the intervention, should have struggled to lose fat mass. In fact they lost 3. The control group did not lose any weight despite an 1. More, testosterone levels usually decrease when thyroid hormones are low . IGF- 1 levels are also decreased in hypothyroidism . Glucagon levels are higher in hypothyroid patients . Sex hormone- binding globulin (SHBG) is low in hypothyroidism . But none of these parameters changed during the LCHF diet. So this diet which was low in carb (8% of calories) and moderately high in protein (3. PUFA (1. 1%) does not seems to affect the thyroid if saturated and monosaturated fat (5. Let’s compare the fatty acid profile of the Volek diet with that of human milk: Saturated. Monounsaturated. Polyunsaturated. Volek diet. 41%4. Human milk. 47. 5%4. Not too much difference. Perhaps PUFA intake needs to be higher than 1. Effects of high fat and thyroid responses to cold. In 1. 94. 5, Mitchell et al published two articles comparing the effects of proteins versus carbohydrates and fat versus carbohydrate on man’s tolerance to cold exposure . Carbohydrate does better than protein, but worse than fat, at maintaining internal temperature as measured by rectal temperature. On the first experiment, five men consumed a high protein diet (4. P, 4. 0% F, 1. 9% C) and five a high carbohydrate diet (1. P, 4. 1% F, 4. 8% C) for 5. Food intake was adjusted to mantain a constant body weight. The effect of decrement in rectal and mean skin temperature during eight hour exposure to cold with light clothing: Rectal Temp. Skin Temp. High Protein. High Carb. 1. 0. 53. Significance. P=0. P=0. 0. 09. 6On the second experiment, five men consumed a high fat diet (1. P, 7. 3% F, 1. 7% C) and five a high carbohydrate diet (1. P, 2. 3% F, 6. 7% C) for 5. Food intake was adjusted to maintain a constant body weight. The excess fat of the high fat group was provided by butter and cream. Decrement in rectal temperature from the first two hour to the last two hours of 6 hours exposures to - 2. Eating a high carb meal between the intervention did not produced any alteration. But, eating a high fat meal cut the decrement in rectal temperature in half. Thyroid hormones are responsible for basal metabolic rate and heat production. So, if a high saturated fat diet maintains body temperature better than a high carbohydrate diet when the body is subjected to cold, it would seem fair to assume that the thyroid functions better on this high saturated fat diet. Conclusion. A diet with sufficient but not excess protein, moderate carbohydrate comprising a minority of calories, and high intake of saturated and monounsaturated fat but low intake of polyunsaturated fat would seem to be optimal for thyroid function. But this is the Perfect Health Diet! References. Is a Low Carb Diet Bad For Your Thyroid? Body composition and hormonal responses to a carbohydrate- restricted diet. Jul; 5. 1(7): 8. 64- 7. Dietary- induced alterations in thyroid hormone metabolism during overnutrition. Nov; 6. 4(5): 1. 33. Effect of low- carbohydrate diets high in either fat or protein on thyroid function, plasma insulin, glucose, and triglycerides in healthy young adults. Protein metabolism during weight reduction with very- low- energy diets: evaluation of the independent effects of protein and carbohydrate on protein sparing. Jul; 6. 2(1): 9. 3- 1. Protein sparing during treatment of obesity: ketogenic versus nonketogenic very low calorie diet. Apr; 4. 1(4): 4. 06- 1. Vegetable Oil and Weight Gain.
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