For about 30 years we’ve had our Governments, health agencies, doctors and dieticians urging us to eat less fat and more carbohydrate. Yet, we now know that many of the fats in the diet, including saturated fat, appear harmless as worst. Some, including the omega-3 fats found in oily fish, look positively beneficial. And on the other wide we also know that excesses of certain carbohydrates (those that are disruptive to blood sugar and insulin) in the diet have some capacity to induce all sorts of ills including weight gain, type 2 diabetes and cardiovascular disease. There is some suggestion that encouraging us to turn away from fat and towards carb is one major factor that is fuelling the burgeoning rates of chronic disease we have seen over the last 3 decades or so.
I was interested to read about a recent study which appears to show quite graphically the potential hazards of applying the low fat/high carb paradigm. In this study, post-menopausal women were asked to increase their carbohydrate intake over a 4 week period. As a result, they ended up eating more starch over the course of the study. The glycaemic index of the diet was increased as well, which essentially means the new diet was more disruptive to sugar and insulin levels. There was some evidence of increased fruit and vegetable consumption over the course of the study too.
First the good news: the subjects lost weight and a measure of antioxidant capacity of the blood was enhanced.
Now, the bad news: the subjects saw significant increases in the level of ‘unhealthy’ blood fats called triglycerides as well as significant decreases in the level of ‘healthy’ HDL cholesterol. The authors of the study conclude In postmenopausal women, following the UK dietary guidelines resulted in changes in the lipid profile that were more likely to favour an increased risk of CHD [coronary heart disease].
While the authors suggest that this may be balanced by the reduced BMI and increased antioxidant status in the body, I suggest that these benefits are also available to those adopting a lower-carb diet. Those adopting a lower-carb diet have the capacity to maintain a high antioxidant status by keeping up a good intake of, say, low-carb vegetables including green leafy ones.
And if a reduction in BMI is what’s required, then it’s perhaps useful to reflect that low-carb diets consistently outperform low-fat ones in the weight loss stakes.
This study, I think, demonstrates at least some of the potential hazards that come with taking conventional dietary advice. And it should serve to remind us of the fact that some carbohydrate sources are not the cosy, wholesome, healthy foods some maintain they are.
Arefhosseini SR, et al. Effect of advice to increase carbohydrate and reduce fat intake on dietary profile and plasma lipid concentrations in healthy postmenopausal women. Ann Nutr Metab. 2009;54(2):138-44.