The LCHF (low carb, high fat) diet has become very popular and works for many people. The diet itself is a good one, but the reasoning behind why it works is severely flawed!
LCHF is said to make you leaner because it increases fat oxidation (a point criticized in earlier posts) and limits the insulin response. Insulin is a hormone which promotes fat storage and is promoted by carbohydrate consumption. The reasoning is that less carbs will lead to less insulin and thus less fat gain. Sounds reasonable right? Unfortunately, the situation is not that simple.
What Does Insulin Do?
Insulin’s main role is to help keep blood sugar levels relatively stable by lowering blood sugar (blood glucose) whenever it gets too high. It does this by lowering the livers ability to produce glucose (gluconeogenesis). When insulin levels PEAK in your blood, it also promotes sugar storage as fat/glycogen. Other hormones, like ASP also have a much more important role in the process of storing sugars as fats, and ASP is stimulated by fat intake, NOT carbs!
Do Carbs or Fats Make Your Fat?
Studies comparing diets with different amounts of fats and carbs have found that the weight gained by these diets is exactly the same no matter how you distribute carbs and fats.
SHORT-TERM fat storage is higher when eating a high fat meal compared to a high carb meal (covered in earlier posts), but LONG TERM the body will even this out and in the end it is the total amount of CALORIES CONSUMED which determines the degree of fat storage.
What About Diabetes?
While there is much we don’t know about diabetes, part of the issue is so called “insulin-resistance” where the body responds less to insulin, resulting in high blood sugar levels as the sugar no longer is able to be taken up and used by the cells. In fact, diabetics have a lower risk of gaining weight for precisely this reason! Insulin resistance can thus be seen as the body’s protection against further weight gain in diabetics. Studies even show that isolated insulin stimulation to the brain leads to weight loss!
So Why Do Diabetics Gain Weight on Insulin?
Some diabetics will require insulin as part of their treatment. This finally allows the body to store the food that you eat. However, whenever insulin is given, blood sugar levels fall to a low, triggering hunger as the body wants to raise blood sugar levels again. Thus, having slightly higher insulin doses than necessary can lead to hunger, over-eating and weight gain. On the other hand, too low insulin levels lead to high blood sugar levels which is associated with more complications in diabetics including kidney failure, nerve damage and visual impairment.
So once again we arrive at the same conclusion when it comes to weight loss. Calories are the most important factor controlling your weight. Other factors, like too low blood sugar due to insulin, can influence how many calories we eat and thus lead to weight loss. Treating diabetes is not easy, which is why it is important to have regular follow-ups with your healthcare practitioner.
Take Home
Don’t worry about the carbs! Worry about overeating, i.e. eating too many calories!
Sources
- Brown PM. Br Med J. 1978 May 13;1(6122):1239-42.
- Hallschmid M. Diabetes. 2004 Nov;53(11):3024-9.
- Schwartz MW. J Clin Endocrinol Metab. 1995 May;80(5):1571-6.
- Int J Obes Relat Metab Disord. 1995 Mar;19(3):175-80.
