Low Fat Versus Low Carb Diet Study - Misleading Pseudoscience

August 24, 2015

Low Fat Diet Loses Weight Better than “Low Carb” - Supposedly! 

 Reference: Cell Metabolism, August 2015,   Washington Post 

 This is a fascinating. A study of exactitude, but with tons of confounding possibilities.   Here is what was done. Nineteen obese adults (BMI of 36 and % body fat around 40%), wanting to lose weight, were admitted to a metabolic unit and fed precisely 2740 calories a day for five days. In that time period, they were fed 50% carbs, 35% fat and 15% protein, more or less the Standard American Diet.   That was baseline. Then, they were switched to a low fat diet, or a low carb diet. Each day they spent an hour in the gym and then fed a precise 30% reduction in calories for the next 6 days. While on the experimental diets they were placed in a sealed chamber that could measure exactly how much carbon dioxide and nitrogen they were putting out. 

The low carb diet reduced carbs from 350 grams a day to 140.   The low fat diet kept carbs at 350 a day and reduced the fat, reducing it from 109 to 17 grams of fat.   Sugar went up in the low fat diet from baseline 152 grams a day to 170, but was still at 37 grams a day in the low carb (that’s over an ounce).    They then repeated the whole cycle on the other diet, switching from low fat to low carb, and vice versa. The low fat diet was shown to lose 110 grams more fat than the low carb folks.   

On average, the study subjects lost 463 grams on the low fat diet, and 245 grams on the low carb diet.   That is about one pound versus half a pound. They did that in 10 days.  When you measure the amount of nitrogen and CO2 you excrete in a metabolic chamber, you can get pretty accurate calculations with error rates down to an ounce, compared to fat measurements by DEXA scan that has a half-pound error rate. 

 What does this study prove?   There have been previous studies showing greater loss with low fat diets, but none for some 20 years. (Rabast)   Our methods of checking multiple data items are also considerably improved since the last go around.   I’m totally fascinated, but I suspect we have some fatal flaws in this study. First of all, the study only last 6 days in each segment. It is useful to give a precise number of calories for science’s sake, but I believe we humans can’t control ourselves that precisely, and carbs stimulate our brains to eat more. 

 But a bigger flaw was calling 140 grams of carbs low carb.   That is lower than 350, but it’s not low.   40 grams of carbs would be low, and 20 is what it takes to really turn on weight loss and turn off insulin.   At 140 grams a day, the subject’s insulin levels actually did decline on the low carb segment, but not to low enough levels (12 to 10). 

 In my teleological explanation, I would maintain that 140 grams of carbs a day is plenty enough to keep insulin up enough to turn on calorie storage – and when combined with high fat, you would expect no weight loss to occur. To me the take away is that you can lose weight if you can control calories precisely. That is the basis of the mail order weight loss programs, or Weight Watchers.   Calories matter and you do have to eat less to lose weight.  

 I have several complaints with this study.   One, I don’t have a mother measuring out precise meals for me, and carbs never fill me up and keep me full. Fat does.   When I eat carbs, I eat too many. Two, this study was 6 days long.   It takes 6 weeks for your body to accommodate to low carbs. Even in fasting, it takes 3-4 days to get to full ketosis.   If this study went longer, it would show the dramatic departure between the two groups on HDL levels, LDL sizes and triglyceride levels. By being only 6 days, we aren’t even over the induction phase of ketosis.   

That makes it fatally flawed, twice. Finally, low carb at 140 grams a day. Ha. Stupid. It’s not a low-carb study. I would state that 140 grams of carbs is enough to keep making sufficient insulin to store fat and carbs, hence nether is reduced sufficiently to lose weight.   (Insulin dropped from 12 to 9.4 – not enough to get to weight loss – aka, an insulin of 5 or less.)   It’s a dumb pseudoscience study. 

 WWW. What will work for me.   I’m going to be more willing to consider precisely measured diet plans, if I can show that they improve cardiac risk factors as well as the low carb does. For now, I’m completely charmed with the effectiveness of low carb at improving cardiac risk factors, Alzheimer’s risk factors, cancer risk factors, weight loss, … did I leave anything else out.   I think this study, making a lot of press media, is really only making misleading noise.   

 Pop Quiz

  1. A low carb weight loss program should probably be at least 40 grams of carbs at the maximum. T or F.                       Answer:  True
  1. On precisely measured calorie counts it is possible to demonstrate that low fat diets lose more fat weight that low carb.   T or F                          Answer:  That’s what this study did, over 6 days, with a 140 grams of carbs as low carb.
  1. 6 days is enough to induce ketosis. T or F                   Answer:  Barely, and probably not always.   In this case not.  Ketosis is burning fat, or losing weight.  If you don't "induce ketosis" you aren't really in a weight loss state.
  1. This study called 140 grams of carbs “low carb”. Atkins would do what?                   Answer:   Roll over in his grave
  1. Carbs are more filling that fat. T or F                     Answer:   False.   Fats make you feel full.
  1. This study proves that low fat beats low carb. T or F                    Answer:   False.   Perfect example of misleading, timid science.