LOW CARB V LOW FAT
The debate of “Low carb” v “low fat diets” has often been described as “the diet war”. Many are firmly in one camp or the other and it is an interesting debate. One that I have grappled with over the last year or so.
A fantastic study came out this week called the “DIETFITS” Randomised Clinical Trial -
Aim - This diet looked the effect of a healthy low fat diet v a healthy low carb diet on weight loss and looked at insulin secretion being related to the effects on weight loss.
Method - 600 people aged 18 to 50 years old without diabetes with a BMI of 28 to 40. Participants were randomly assigned to either low carb group or low fat group. They had 22 diet specific small group sessions delivered by health educators who taught on behaviour modification over 12 months. In these sessions they also covered physical activity, emotional awareness and behaviour modification. -
The Diets - Both diets had 2 key stages
1.Limbo Stage – first 8 weeks they could only have 20g a day of the macronutrient they were meant to have low (eg low carb had 20g of carbs and low fat 20g of fat)
2.Titrate stage – after that 8 weeks added in 5 to 15g/d per week until they reached the lowest level of fat or carbs that they believed they could maintain.
Diet Quality was key - Both diets focused on quality - to maximise vegetable intake, minimise sugars, refined flours and trans fats and focus on whole foods that were minimally processed, nutrient dense and prepared at home when possible.
1. No significant difference between low carb and low fat groups in terms of weight loss (worth noting some didn’t lose any weight and some gained weight)
2. Total energy was approximately 500-600 kcal/d lower for BOTH groups (without them actually being told to do this.)
3. Secretion of insulin made no difference to weight loss
4. Some difference in the groups - LDL cholesterol (bad cholesterol) was lower in low fat group but the low carb group had higher HDL (good cholesterol) and low triglyceride level (high TG would mean higher risk of cardiovascular disease) -
Summary - see next comment