Low Carb Beats Low Fat Again, Annals of Internal Medicine article

Once again, a randomized trial demonstrates that a carbohydrate restricted approach is superior to a low fat diet with regards to weight loss, inflammation, body composition and cardiovascular risk factors. This study was recently published in the Annals of Internal Medicine, the official journal for the American College of Physicians.

Men and women aged 22 to 75 years with a body mass index of 30 to 45 kg/m2 (obesity defined as BMI > 30, morbid obesity defined as BMI >35) were recruited from the general public by using mailing lists, fliers, work site and community screenings, and television advertisements.

Neither diet included a specific calorie or energy goal. Participants in each group were asked to refrain from changing their physical activity levels during the intervention

Here is the summary cut and pasted from the abstract.

Objective: To examine the effects of a low-carbohydrate diet compared with a low-fat diet on body weight and cardiovascular risk factors.

Design: A randomized, parallel-group trial. (ClinicalTrials.gov: NCT00609271)

Setting: A large academic medical center.

Participants: 148 men and women without clinical cardiovascular disease and diabetes.

Intervention: A low-carbohydrate (<40 g/d) or low-fat (<30% of daily energy intake from total fat [<7% saturated fat]) diet. Both groups received dietary counseling at regular intervals throughout the trial.

Measurements: Data on weight, cardiovascular risk factors, and dietary composition were collected at 0, 3, 6, and 12 months.

Results: Sixty participants (82%) in the low-fat group and 59 (79%) in the low-carbohydrate group completed the intervention. At 12 months, participants on the low-carbohydrate diet had greater decreases in weight (mean difference in change, −3.5 kg [95% CI, −5.6 to −1.4 kg]; P = 0.002), fat mass (mean difference in change, −1.5% [CI, −2.6% to −0.4%]; P = 0.011), ratio of total–high-density lipoprotein (HDL) cholesterol (mean difference in change, −0.44 [CI, −0.71 to −0.16]; P = 0.002), and triglyceride level (mean difference in change, −0.16 mmol/L [−14.1 mg/dL] [CI, −0.31 to −0.01 mmol/L {−27.4 to −0.8 mg/dL}]; P = 0.038) and greater increases in HDL cholesterol level (mean difference in change, 0.18 mmol/L [7.0 mg/dL] [CI, 0.08 to 0.28 mmol/L {3.0 to 11.0 mg/dL}]; P < 0.001) than those on the low-fat diet.

Limitation: Lack of clinical cardiovascular disease end points.

Conclusion: The low-carbohydrate diet was more effective for weight loss and cardiovascular risk factor reduction than the low-fat diet.

Primary Funding Source: National Institutes of Health.

Let’s go through those results again: At 12 months, participants on the low-carbohydrate diet had

  1.  greater decreases in weight. This has been demonstrated in multiple previously published studies.
  2.  greater decreases in  fat mass. This is an important distinction, the low carb group lost more fat, not muscle.
  3.  greater decreases in the ratio of total to high-density lipoprotein (HDL) cholesterol. This ratio is a measure of cardiovascular risk (risk for heart attack and stroke). It improved more on low carb than on low fat diets.
  4.  greater decreases in triglyceride level. Triglyceride level is also an important cardiovascular risk factor. It went down significantly more as compared to the low fat diet.
  5.  greater increases in HDL cholesterol level. This result is considered to be protective against heart attack and stroke.
  6. greater decreases in CRP level than those in the low-fat group. CRP (C-reactive protein) is a blood test for inflammation and is also a cardiovascular risk factor.
  7. significant decreases in estimated 10-year risk for coronary heart disease as measured by the Framingham risk analysis at 6 and 12 months, whereas those in the low-fat group did not. Say again, the low fat group did not decrease their Framingham risk analysis but the low carb group did.

All of these differences were “statistically significant”, meaning they were unlikely caused by accident.
And what about side-effects?

The number of participants who had symptoms, including constipation, fatigue, thirst, polyuria, diarrhea, heartburn, gas, nausea, vomiting, appetite changes, or headache, did not differ significantly between the low-carbohydrate and low-fat groups, except significantly more participants on the low-fat diet reported headaches at 3 months

The authors concluded:

Our study found that a low-carbohydrate diet induced greater weight loss and reductions in cardiovascular risk factors at 12 months than a low-fat diet among black and white obese adults who did not have diabetes, CVD, or kidney disease at baseline. Compared with a low-fat diet, a low-carbohydrate diet resulted in greater improvements in body composition, HDL cholesterol level, ratio of total–HDL cholesterol, triglyceride level, CRP level, and estimated 10-year CHD risk. Because CVD is the most common cause of death in the United States and obesity is a particularly prevalent risk factor, our study has important clinical and public health implications

Effects of Low-Carbohydrate and Low-Fat Diets: A Randomized Trial, A. Bazzano, MD, PhD, MPH et. al., Ann Intern Med. 2014;161(5):309-318. doi:10.7326/M14-0180

Get rid of the sugar-added foods, processed and refined flour foods and vegetable oils. Send a message to corporate America that crap-in-a bag and crap-in-a-box is no longer in demand. Eat only grass-fed meat, wild seafood, fresh vegetables, fresh fruit and tree nuts. Enjoy better health and better food.

 

Bob Hansen MD.

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