By @JohannWindt, @Liam_West & @AniaTarazi
Attendees of the 2015 Old Mutual Health Convention were fattened with four full days of low-carb, high fat (#LCHF) information #PunIntended. For brief summaries, see daily blogs of Day 1, Day 2, and Day 3. Combining our notes, conference speaker interviews, and your questions, #TeamBJSM hope this blog captures and summarizes the main scientific research presented at the summit. We have hyperlinked relevant papers in green for you to make up your own mind about the diet – #NoBias. There will be two parts: “#LCHF and #Health” and the second, “#LCHF and Performance”. Here, in part 1, we look at LCHF in respect to weight loss, cardiovascular risk and glycemic control and answered the common misconceptions about the diet.
#LCHF AND #HEALTH
#LCHF for weight loss:
Physiological Basis – Hormonal Model Adopted – The central basis of the low-carbohydrate diet is adoption of the hormonal model of obesity, as opposed to a strictly energy balance model. They suggest that a purely calorie-based model (energy in vs. energy out) is insufficient, and the interplay of dietary intake, hormonal and physiological responses is key to understanding weight control. Most speakers highlighted the role of dietary carbohydrates in raising insulin levels, thereby encouraging the body to store fat (de novo lipogenesis), and block fat breakdown (lipolysis). Support for this model includes differential weight loss in isocaloric conditions, and different weight loss in low-carbohydrate vs. low fat diets, dependent upon insulin resistance. Bonus reading here & here.
Trial Evidence – Low Carbohydrate Diets vs. Other Diets – A number of speakers presented evidence that low carb diets have outperformed low-fat diets (related reading; one, two, three) and low glycemic index diets in randomized trials of weight loss. This observation has been picked up in a number of systematic reviews regarding the efficacy of low carbohydrate diets – links to read here; one, two & three. Notably, it was identified the low-fat diets were deliberately energy controlled (with prescribed kcal to induce weight loss), while the low-carbohydrate diets were unrestricted in energy intake, yet still outperformed low-fat counterparts.
Caveats and Misconceptions – First a calorie is a calorie. It’s a unit of energy, it measures the potential energy food can release. Therefore #CaloriesStillCount. But, it must be emphasised, two equal calories can produce different biological effects to body fat or body weight, i.e. a calorie of protein vs a calorie of refined carb. Second, carb intake leading to fat storage is an oversimplification. Dr. Jason Fung aptly presented that the “carbs leading to insulin leading to fat” hormonal model is a part of the puzzle, but fails to take into account all aspects. With the cycle of increased serum insulin, leading to insulin resistance, causing higher serum insulin, etc. at the center of the model, he identified three central players that all link to Insulin:
- Carbohydrates – As often identified in the hormonal model above, cause increased insulin levels and can if consumed in too high quantities and frequencies, contribute to insulin resistance.
- Fiber – Helps reduce insulin levels #Protective – see papers here – one & two
- Fructose – Unique capacity to induce insulin resistance, thereby exacerbating the problems.
Since the refining/processing of foods often strip the fiber from foods, and add additional fructose, they are especially harmful in inducing weight gain. #CheckFoodLabels
Therefore, the consistent take-home messages from the conference in terms of weight control included #RestrictCarbs, #EatRealFood, & #AvoidProcessedFoods.
#LCHF and cardiovascular risk:
Conventional wisdom states that too much fat increases fat and cholesterol in the bloodstream, and contributes to cardiovascular risk – commonly called the diet-heart hypothesis. If true, a LCHF diet is a tremendous risk, and will predispose people to heart attacks and CVD. However, these fears must be reconsidered in light more recent data.
Systematic reviews – click on one, two & three to view – examining the LCHF diet and cardiovascular risk factors, showed significantly:
- Improved weight, BMI and waist circumference
- Increased HDL, which serves as protective against heart disease
- Decreased triglyceride levels
- Decreased systolic and diastolic blood pressure
- Decreased fasting plasma glucose
- Decreased Insulin levels
- Decreased HbA1c levels
Further evidence also suggests:
- Reduced levels of saturated fats in the bloodstream
- Reduced inflammatory biomarkers
The ‘red-flags’ to patients on a LCHF diet is the variable response of LDL levels, and average increase in total cholesterol levels. In terms of total cholesterol increases, this is predominantly or exclusively due to HDL increases, serves as protective to CVD, and is not seen as a major concern. Though the average LDL level is usually unaltered, it must be taken into account with a LCHF diet and CVD. It was pointed out that LDL levels are only one component of CVD risk, the rest of which all improve on LCHF. In addition to this, the particle sub-fractions of LDL change positively in response to LCHF, not negatively – check out two interesting papers here & here. Nonetheless, total cholesterol and LDL responses on a LCHF diet are variable, and more research will have to investigate these parameters.
To wrap up, cardiologist Dr. Aseem Malholtra identified that the best evidence to date for primary prevention of CVD is for the Mediterranean diet from the PREDIMED study; with the supplementation of EVOO and raw nuts and total of 41% fat content. He recently highlighted that saturated fat is not the major issue, and data on LCHF diets and CVD risk factors lend support to their safety from a CVD standpoint.
#LCHF and Glycemic Control:
LCHF diets effectively reduce body weight, insulin levels, fasting glucose levels, reduce insulin resistance, and significantly reduce HbA1c – evidence to back this up? Read 2 papers here & here. Hence, they are extremely effective in improving glycemic control and type 2 diabetes.
Dr. Jason Fung addressed the underlying issue of insulin resistance in T2DM, highlighting the fact that controlling blood sugar levels through intensive glucose lowering in diabetic patients has little benefit on mortality. He stated that a focus on blood sugar levels, as a chronic, progressive disease promotes learned helplessness and fails to take the current evidence into account. He highlights that both bariatric surgery and fasting/extreme energy restriction have potent effects in reducing insulin resistance and reversing diabetes. Similarly, efforts should be made to control insulin levels and reduce the underlying insulin resistance through dietary strategies. This can best be achieved through restricting refined carbohydrates, increasing fiber intake, and removing fructose from the diet.
As expected, the national dietary guidelines of were touched on by a number of the speakers, including Gary Taubes and predominantly Zoe Harcombe. Presenting her recent paper, she highlighted that the randomized trial evidence at the time of the national guideline introductions in the US and UK was insufficient to prescribe a low-fat message.
An overarching theme of the conference was that ‘one-size-fits-all’ dietary guidelines that continue to restrict fat and cholesterol intake are not fair to the existing evidence. As discussed, Mediterranean diets with over 40% fat intake have continuously shown positive health outcomes. Furthermore, #LCHF diets reduce weight, cardiovascular risk, and glycemic control. This differs from the guideline recommendations.
Below we have tried to briefly address some #LCHF common misconceptions
“#LCHF treats all food as the same, as long as carbs are controlled”:
- Consistently, all speakers presented that nutrients should come from #Unprocessed #RealFood, with high nutrient density and minimal processing.
- All carbohydrates are the not the same, and intake should come from whole, unprocessed foods, green leafy vegetables, cruciferous vegetables, and minimal fruit.
- Fats are not all the same. Mono and saturated fats are recommended on a #LCHF diet, while polyunsaturated sources should not be consumed in high quantities.
“What about Ketosis?”
- Nutritional ketosis and diabetic ketoacidosis are entirely separate physiological states #Important
- Nutritional ketosis has a blood ketone level of 0.5-2.0 mmol/L, with post-exercise ketosis up to about 3.0
- Starvation ketosis can elevate levels up to 5.0-7.0 mmoL/L.
- Ketoacidosis occurs with levels of 10 mmol/L or more
- Ketones can serve as a primary fuel source for the brain during carbohydrate restriction.
- There is emerging evidence for the benefits of ketogenic diets in various health conditions, including epilepsy, neurogenerative diseases, cancer, polycystic ovary syndrome, to name a few – see the evidence here, here & here.
- Nutritional ketosis has a blood ketone level of 0.5-2.0 mmol/L, with post-exercise ketosis up to about 3.0
“Higher saturated fat intakes on low-carb diets would cause higher saturated fats in bloodstream”
- Saturated fat circulating in the blood is dangerous, but dietary intake of saturated fat does not result in higher blood saturated fat levels (11)
- A substantial body of evidence – see here, here & here – has built up against the low-fat dietary guidelines. Saturated fat intake is not a major health problem as previously presented.
“Excess protein intake on a low-carb diet is dangerous”
- Most low carbohydrate diets are moderate protein diets, with 15-25% of calories coming from protein.
“#LCHF insists that low-carb diets are universally the best diet”
- Individual responses to low-carb diets vary, meaning #LCHF does not suit all! However, they should be considered as a safe, viable dietary option.
- Insulin resistance can be reduced with a low-carb diet. Therefore, those with insulin resistance of type 2 diabetes may respond more favourably to a low-carb diet than those who have greater insulin sensitivity.
“Nutrient density is low on a low-carb diets”
- If a #LCHF diet is followed as recommended at the conference (i.e. #RealFood, #Unprocessed), nutrient density will be attained through intake of a variety of vegetables, meat, and dairy. If attention is paid to eating whole foods from a variety of sources, all the micronutrients that would be attained on a high carb can be attained on a #LCHF diet.
Alongside a ‘well-formulated’ ketogenic diet, as described by Drs. Westman and Phinney, some additional sodium and magnesium intake may be recommended to help to prevent muscle cramps in susceptible individuals.
In Part 2 of ‘To#LCHF or not to #LCHF’ we’ll take a look at “LCHF and Performance”. Starting with the view of a LCHF diet on endurance performance and the need for an adaption period. We’ll take a look at the pros and cons of the summit and our take home message from #LCHF2015.
Johann Windt BHK CSCS (@JohannWindt) is a graduate student at the University of British Columbia in the Department of Experimental Medicine. His research currently focuses on physical activity prescription and lifestyle counseling in family medicine settings. A certified strength and conditioning coach, Johann is passionate about improving health, body composition, and performance through evidence-based application of nutrition and physical activity.
Dr. Liam West BSc (Hons) MBBCh PGCert SEM (@Liam_West) is a Cardiff Medical School graduate and now a junior doctor at the John Radcliffe Hospital, Oxford. He is an Associate Editor for BJSM and also coordinates the “Undergraduate Perspective on Sports & Exercise Medicine” Blog Series.
Ania Tarazi BSc (Hons) (@AniaTarazi) coordinates the Aspetar Sports Medicine Journal in Doha, Qatar. Ania graduated from Royal Holloway University of London with an International Business degree in 2013. Her interests lie in social media engagement to promote physical activity and healthy eating in children.