In the popular press recently there have been many articles and opinion pieces that support a reduced carbohydrate/high fat diet. In May, a seemingly authoritative report from the UK’s National Obesity Forum received worldwide coverage, giving the appearance that a number of prominent health professionals endorsed the consumption of fat and reduction of carbohydrates to combat the obesity and diabetes crisis.
This report caused concern and confusion for many people struggling with their weight and/or trying to manage their type 2 diabetes. Superficially this report looks credible due to the authorship, but it is worth considering two matters overlooked in most media reports.
First, it was published as a report rather than a peer-reviewed study in a scientific journal. After the publication, many eminent health professionals and nutrition experts including Professor Mann, from the University of Otago, commented that research articles with evidence contrary to the authors’ stance were not included in this report, and the report lacked balance in how it reported the papers that it had cited.Second, the report’s hypothesis is that healthy eating has “failed” and that this is the cause of the obesity epidemic. But many national and international diet surveys show that most people don’t follow the recommended healthy eating guidelines in the first place.
In New Zealand, for example, we typically eat too much high fat and high sugar foods, and fail to get enough vegetables, fruit and fibre. This is why we have an obesity problem.Reduced carbohydrate diets can result in weight loss. Weight loss will occur with any energy intake restriction, regardless of how it is achieved.
But long-term studies of those following restricted carbohydrate diets show that they are no more effective than a healthy eating approach after 12 months.
Why is this? Quite simply, to be successful at weight loss, the energy restriction must be sustained through long-term behaviour change (ie you have to stick to the diet) and humans are poor at long-term behaviour change.
So, if both healthy eating and reduced carbohydrate diets are challenging to stick to, why should we follow the healthy eating recommendations such as those in the Ministry of Health’s Eating and Activity Guidelines for New Zealand Adults, in preference to a reduced carbohydrate approach?
One good reason is that healthy eating has been shown in research to be better at reducing the metabolic problems that lead to and contribute to the health consequences of type 2 diabetes.A number of the Ministry of Health’s healthy eating recommendations focus on reducing the total amount of saturated fat in the diet.
High saturated fat intakes are linked with increased insulin resistance and cardiovascular disease. Some recent research suggests there may be little relationship between saturated fat intake and heart disease death rate, however that same research highlighted that high saturated fat intake was linked with greater disability from cardiovasular events, and the researchers continued to support a reduction in saturated fat in the diet.
Following the Ministry’s healthy eating recommendations will also result in a reduction of “free sugars” in your diet. Free sugars are “those sugars added during manufacturing, preparation and consumption and those from juices, honey and syrups.” This advice, while not as strict as the “no sugar” approach of many reduced carbohydrate diets is likely to be more sustainable. A reduction in free sugar intake will result in reduced glycaemic load and lower post-meal blood glucose levels, reducing the complications of diabetes.
The Ministry’s healthy eating guidelines also encourage the consumption of a high-fibre diet through eating a wide range of vegetables and fruits, plus wholegrains. Eating a high-fibre diet with a focus on wholegrains will reduce the glycaemic load, and improve cholesterol levels for people with diabetes. In addition, recent research on fibre and gut bacteria suggests a healthy gut microflora may reduce the risk of both heart disease and diabetes through reducing inflammation, so increasingly we are focusing again on high fibre being key to health improvement, something that is difficult to achieve on a reduced carbohydrate style diet.
So before you go on a reduced carbohydrate/high fat diet, please consider this:
All behaviour change is challenging, so any changes to your diet should be spent on something you can stick with most of the time for the long term.
Healthy eating (as described in the Ministry of Health’s guidelines) will reduce many of the risk factors associated with diabetes and cardiovascular disease. This kind of eating is not the cause of the obesity epidemic, it is our best chance of leading a healthy lifestyle.