Understanding the New NLA Scientific Statement on Low-Carbohydrate (Ketogenic) Diets in Under 5 Minutes
The rising rates of obesity and Type 2 diabetes mellitus are responsible in part for the surging interest in diets described as “low-carb”, low-carbohydrate, and ketogenic. The popularity with the public is due in part to some high-profile actors, sports figures and media-friendly health experts but has the scientific evidence grown as rapidly as the headlines?
To evaluate this objectively, the National Lipid Association (NLA) reviewed the existing science and presented a scientific statement that was recently published online. The key takeaways of the statement were summarized in a press release as indicating that:
- Low- and very-low-carbohydrate diets, including ketogenic diets, are not superior to other weight loss diets and may severely restrict nutrient-dense foods that offer cardiovascular benefits.
- While they may have advantages on appetite and reducing triglyceride levels and diabetes medication use, current evidence showed mixed effects on low-density lipoprotein cholesterol levels.
- There is no clear evidence for advantages related to other cardiometabolic risk markers.
- While some patients prefer a low-carbohydrate eating pattern, which may be reasonable for short periods of time (<6 months), long-term compliance is challenging, and long-term benefits and risks are not fully understood.
- Regardless of the weight loss strategy chosen, a patient-clinician discussion about the risks and benefits and patient preference is of vital importance, since many patients follow the diets without medical supervision, which can increase the risk of adverse effects.
As not all will read the entire document, and the importance of the statement is high, a brief overview of the conclusions of the NLA on low-carb diets (LCD) is timely.
1. Definition of LCD
Very low-carb, high fat diets capable of inducing ketosis were defined separate from moderately low-carb diets based on the total daily energy (calories) and the % of calories or grams/day derived from carbohydrate macronutrients.
2. LCD and weight loss: Key Points
Short-term (≤6 months) hypocaloric low-CHO and very-low-CHO diets may result in greater weight loss than hypocaloric (high-CHO, low-fat) HCLF diets.
Longer-term (>6 months) results suggest that low-CHO and very-low-CHO diets may result in weight loss that is equivalent to that of HCLF diets.
Very-low-CHO diets are difficult to maintain and are not clearly superior for weight loss compared with diets that allow a higher amount of CHO in adults with overweight and obesity with or without diabetes.
Long-term participation in any weight loss intervention is difficult, but adherence to the assigned macronutrient distribution (ie, CHO, protein, and fat) is lower with low-CHO and, especially, very-low-CHO diets.
Personal preference should be considered when selecting a weight loss diet.
3. LCD and Body Composition: Key Points
Ketosis is associated with initial body water loss.
The initial weight loss that occurs with low-CHO diets and very-low-CHO diets/KDs is primarily due to loss of body water.
All weight loss interventions using CHO-restriction appear to result in greater loss of lean body mass (LBM) compared with more macronutrient balanced hypocaloric diets.
Higher protein content in low-CHO diets may result in less LBM loss during weight loss.
4. LCD and Risk Factors for Heart Disease: Key Points
Results from meta-analyses demonstrate a variable total-C and LDL-C response to low-CHO and very-low-CHO diets.
A high saturated fatty acid (SFA) content in low-CHO and very-low-CHO diets is a key factor for an increase in LDL-C.
Compared with high-CHO, low-fat (HCLF) diets, low-CHO diets generally decrease TG levels.
Compared with HCLF diets, low-CHO diets generally result in a short-term increase in HDL-C levels, which is typically not maintained for longer durations.
Improvements in TG and HDL-C levels were achieved at low- and moderate-CHO intakes vs very-low-CHO intakes, which may result in better long-term adherence.
Genetic factors have been shown to play a role in the individual variability of LDL-C levels with low-CHO and very-low-CHO diets.
Baseline and follow-up lipid/lipoprotein assessment are essential for individuals following low-CHO and very-low-CHO diets to identify extreme responses.
5. LCD and Glycemic Disorders: Key Points
Low-CHO diets did not reduce FBG or insulin levels more than high-CHO, low-fat (HCLF) diets in clinical trials.
Low-CHO diets result in a greater short-term reduction in HbA1c vs HCLF diets, but there were no differences between diets beyond 1 year.
Low-CHO diets resulted in a reduction in the use of diabetes medications, and reductions in the use of diabetes medications were achieved at CHO intake levels that do not induce ketosis.
The Mediterranean dietary pattern produced improvements in TG, HDL-C, and HbA1c levels in individuals with T2D compared with low-CHO diets.
6. LCD and Safety Concerns Including Mortality
Close medical supervision is essential for individuals with ASCVD, risk of atrial fibrillation, or the presence or history of heart failure, kidney disease, or liver disease who choose to follow a very-low-CHO diet/KD.
VLCHF/KDs are contraindicated in patients with a history of hypertriglyceridemia-associated acute pancreatitis, severe hypertriglyceridemia, or inherited causes of severe hypercholesterolemia.
Individuals with T2D should receive medical supervision and cardiometabolic monitoring while on very-low-CHO diets/KDs.
Low-CHO and very-low-CHO diets can lead to hypoglycemia or hypotension and may require adjustment in diabetes or HTN medications.
Patients taking SGLT2 inhibitors should avoid very-low-CHO diets/KDs because of an increased risk of SGLT2 inhibitor–associated ketoacidosis.
More frequent monitoring of vitamin K–dependent anticoagulation therapy may be required with very-low-CHO diets due to the potential change in vitamin K bioavailability and its effect on anticoagulation therapy.
Both low- and high-CHO intake has been associated with a higher risk of mortality in the general population; moderate-CHO intake has been associated with the lowest risk of mortality in the general population.
7. Conclusions on LCD: Key Points
There should be a clinician-patient discussion regarding need for and oversight of low-CHO diets or very-low-CHO diets/KDs before initiation.
Low-CHO and very-low-CHO diets may be an option for a short-term initial weight loss period (2–6 months).
For long-term weight maintenance and cardiovascular health, it is recommended to gradually increase CHO intake. An emphasis should be placed on CHO foods associated with reduced cardiometabolic risk, including vegetables, fruits, whole grains, and legumes.
A comprehensive lifestyle intervention program includes reduced calorie intake, increased physical activity,
and behavior change therapy to facilitate weight loss or maintenance of reduced body weight.