Low(er) Carb Beats High Fiber

Nutrition Journal Randomized Trial

It would be interesting to know if the participants were rated for appetite during the study.  Otherwise, results are as would be expected.  Interesting to note that carbs were not particularly low on this study - 40% of caloric intake, with 30% of intake as protein, in other words, Zone Diet proportions - nor was protein "high" except as relative to other diets. 

Dr. Robert Lustig, of "Sugar:  The Bitter Truth" YouTube fame (which is a long, but fascinating video), likes to say something along the lines of "it's either fat or fart."  It's a bit of an awkward attempt, but he's trying to articulate his deep conviction that eating high fiber foods is the be all end all for weight loss and health.  He's right - if you MUST eat carbs, eating high fiber carbs is better than otherwise.  If you eat enough insoluble fiber, some will survive the trip through the gut to the "back end" of the digestion process before being broken down, leading to some 'noxious emissions' (not yet controlled by the EPA, but perhaps that's in our zero emissions future).

I recommend just saying no to the current "the more the better" attitude towards fiber.  I've yet to see significant evidence that fiber does anything more than make you 'noxious.'  If you are eating meat, vegetables, nuts and seeds, some fruit, little starch and no sugar/wheat, you don't need "more fiber."  I'm pretty sure the human genome didn't evolve to make you dependent on copious fiber consumption day in a nd day out, and it's becoming more and more clear that the folks that fell in love with the idea of fiber will not be able to demonstrate that the object of their affection is actually beneficial. 

Background

Studies have suggested that moderately high protein diets may be more appropriate than conventional low-fat high carbohydrate diets for individuals at risk of developing the metabolic syndrome and type 2 diabetes. However in most such studies sources of dietary carbohydrate may not have been appropriate and protein intakes may have been excessively high. Thus, in a proof-of-concept study we compared two relatively low-fat weight loss diets - one high in protein and the other high in fiber-rich, minimally processed cereals and legumes - to determine whether a relatively high protein diet has the potential to confer greater benefits.

Methods

Eighty-three overweight or obese women, 18-65 years, were randomized to either a moderately high protein (30% protein, 40% carbohydrate) diet (HP) or to a high fiber, relatively high carbohydrate (50% carbohydrate, >35g total dietary fiber, 20% protein) diet (HFib) for 8 weeks. Energy intakes were reduced by 2000 - 4000 kJ per day in order to achieve weight loss of between 0.5 and 1 kg per week.

Results

Participants on both diets lost weight (HP: -4.5 kg [95% confidence interval (CI):-3.7, -5.4 kg] and HFib: -3.3 kg [95% CI: -4.2, -2.4 kg]), and reduced total body fat (HP: -4.0 kg [5% CI:-4.6, -3.4 kg] and HFib: -2.5 kg [95% CI: -3.5, -1.6 kg]), and waist circumference (HP: -5.4 cm [95% CI: -6.3, -4.5 cm] and HFib: -4.7 cm [95% CI: -5.8, -3.6 cm]), as well as total and LDL cholesterol, triglycerides, fasting plasma glucose and blood pressure. However participants on HP lost more body weight (-1.3 kg [95% CI: -2.5, -0.1 kg; p=0.039]) and total body fat (-1.3 kg [95% CI: -2.4, -0.1; p=0.029]). Diastolic blood pressure decreased more on HP (-3.7 mm Hg [95% CI: -6.2, -1.1; p=0.005]).

Conclusions

A realistic high protein weight-reducing diet was associated with greater fat loss and lower blood pressure when compared with a high carbohydrate, high fiber diet in high risk overweight and obese women.