A new study just came out the other day in the Journal of the American College of Nutrition by Virginia Tech researchers that compared a low-carb, high-fat (LCHF) Atkins diet (>65% fat) with a low-fat, high-carb (LFHC) AHA (American heart association) diet (15% pro, 20% fat, 60 % carbs).
The diets were followed for 4 weeks by 29 pre-menopausal (age 32-45), overweight women, sedentary women, with no disease (i.e. diabetes) or other endocrine disorders.
The women came to the lab every week at the same time to have blood, urine, body weight and waist circumferences measured. Blood was collected to look at classic disease risk markers, including high-sensitivity CRP which is a protein in our blood that increases when we are sick, when we have systemic inflammation, and it may help predict our risk for heart disease. High CRP is usually seen in obese persons. It is shown to decrease with weight loss, diets high in fiber, diets high in antioxidant foods (like fruit) and diets low in simple high-glycemic carbohydrates.
Urine was collected to look at an isoprostane, which is an inflammatory compound produced in the body from arachidonic acid and is a classic marker of oxidative stress(OS). OS is an imbalance between production and elimination of reactive oxygen species (ROS) which are compounds that have an unpaired electron on oxygen and can attack other molecules in the body. ROS are associated with many diseases and with ageing.
The results showed that after 4 weeks, all women lost a significant amount of weight, but the women in the LCHF group lost more than in the HCLF group (8 lbs vs 5 lbs), especially during the first week. For some reasons, the circumferences were not reported. Caloric intake between the two groups was similar except that the macros were obviously different. They both consumed on average about 1350 to 1400 calories.
The diets had no effect on isoprostane production, and no differences were noted between groups. This means that the diets did not increase oxidative stress.
However, what they did find after 4 weeks that was different and which was surprising to me, was that the LCHF diet increased concentrations of CRP (from 5.7 mg/L to 7.1 mg/L) whereas the HCLF diet decreased CRP (from 4.8 mg/L to 2.7 mg/L). But, this increase and decrease was not completely linear. The LCHF started at 5.7, then went to 7.5, 6.1, 6.1 and 7.1. The HCLF started at 4.8, then went to 4.2, 4.3, 4.1, and 2.7 in the last week. If the results were looked at the third week, there wasn't any difference. But, that wasn't the case.
Plus, in speaking with other people who know more about CRP than I do, they state that CRP does not increase like it did here unless there was illness among a few of the women. Many times, when a women changes her diet drastically to lose weight, she ends up sick with a cold, so that may explain these results. Further, please keep in mind that the normal values for CRP are less than 1.0 mg/L for the lowest risk of heart disease, 1.0 to 3.0 mg/L for average risk, and more than 3.0 mg/L is the highest risk. In this study, the women all started with an apparently higher risk, but again, this number is increased in those who are very overweight, those who have previously exercised, and those that are sick, or are getting sick (i.e. a cold).
Even though CRP was elevated, it was not associated with an increase in an inflammatory cytokine called IL-6. This cytokine is thought to induce release of CRP from liver, but it's relationship to CRP is not simplistic. Some studies find that IL-6 and CRP change in the same direction with dietary alteration, while others do not find this effect. Usually, CRP drops with weight loss, but IL-6 does not always.
Overall, what is the explanation for these findings? Does this mean that women should not follow a LCHF diet to lose weight because it will increase their CRP levels? No, and this is why:
· First, here at UConn, we have conducted this same type of investigation in men and women, comparing a HCLF diet with a LCHF diet and have not seen an elevation in CRP. The difference between our studies and this one though is that our studies are carried out for a longer period of time; usually at least 6 weeks, but mostly 12. When a person is given more time to adapt to a diet, it will help their body return to normal homeostasis. Think about it: If you radically changed your diet from low-fat to ultra-low carb, do you think it would automatically respond favorably? No. At first your body would have to make many modification in various enzymes and proteins before it was completely normalized to the new diet. Four weeks is not enough time to see the true effects of a radical dietary change like this one.
· Second, if you look at the individual results in CRP, you can see that there were a few women only in the LCHF group (Atkins) that had quite high CRP levels. This would drag the norm up. Some women were as high as 17 mg/L at baseline. Then, after the 4 weeks, only 2 women really had a spike in CRP. Their values went up by 5 and 6%, which is more likely a result of some infection or illness, not because of the diet. These are probably women who were not suited well for the diet, and perhaps they got so stressed out about eating so much fat that they made themselves sick.
· Third, weight loss was greater in LCHF versus HCLF and from the research we've conducted, this loss is mainly visceral fat. When you lose weight from deep adipose tissue stores, it means that a lot of fat is released into the blood. Some investigators feel that these free fatty acids are pro-inflammatory which would then result in increased CRP.
· Fourth, no other markers of inflammation were associated with CRP, not IL-6, and not the isoprostanes. This further supports the fact that CRP, which is increased short term in response to infections and illness, was not due to the diet alone. It had to do with some of those women responding negatively, either with stress or illness.
· Fifth, ultimately, it may boil down to the fact that these women were not suited to follow a very low carb diet. In our research and in other studies, it is shown that women with risk factors for Metabolic Syndrome including central obesity (i.e. belly fat, the apple shape), increased insulin and glucose (indicating poor carb tolerance), low HDL cholesterol, high blood triglycerides, and high blood pressure, are the ones that respond best to carbohydrate restriction. For other women with gluteal-femoral fat (i.e. the pear shape), good carbohydrate tolerance, and low triglycerides, the low carb approach does not work very well.
Overall, this drives home the idea that you have to follow a diet that is best for your body, not one that is popular at the time. Realize first if you really need to restrict carbohydrates, instead of just blindly following the ultra-low carb diet revolution bandwagon. Some women do not need to drop carbs this low to see weight loss and fat loss. Then, don't assess your results in just the first 4 months. It takes time to lose weight, fat and improve your health. If you developed love handles and a tummy in 4 months, don't think it's going to come off in 4 weeks. On that same note, if you radically change your diet around from low fat to low carb, don't think your body is going to be happier right away. Give it time to adjust and learn to use fat effectively.
Thoughts and feedback are welcomed.