Which diet is the answer for effective obesity treatment?

Obesity is an epidemic in the modern developed world due to an increase in highly processed foods and a saturation of high sugar / high fat food products onto the market, combined with an increasingly sedentary lifestyle. Most weight loss programs can be placed into three categories: low calorie diets, low fat diets and low carbohydrate/high protein diets. When analysing these diets it is important to look at whether or not they achieve weight loss and more importantly is this weight loss maintained over time.

Put simply, if calorie intake is less than calorie expenditure for a significant period of time, weight loss will occur. Diets that focus on reduced calorie intake will generally achieve weight loss, however the question is what kind of calories are being consumed? For instance, drinking wine for the entire day will provide calories. So there must be emphasis on nutrient dense calories and a balance of carbohydrates, proteins and fats so that healthy body function is maintained. The question to ask is: Is this diet providing satiety and if not, is it likely that this diet will be maintained over time.

There has been a recent increase in popularity of low carbohydrate diets over low fat diets. A meta-analysis of all studies between 2003-2006 comparing the two diets concluded that “low carbohydrate, non-restricted diets appear to be at least as effective as low-fat, energy-restricted diets in inducing weight loss for one year” (Nordmann, Nordmann & Briel, 2006, p. 287).  It has been noted that patients on low carbohydrate diets tend to lose more weight in the first few months than low fat diets. This may be due to the fact that “energy expenditure increases when higher protein intake replaces carbohydrates” (Foreyt, Salas-Salvdo, Caballero, Bullo, Gifford, Bautista & Serra-Majem, 2009, p.S 100). It may also be due to depletion of glycogen stores, which is associated with water loss so the weight loss is not due to loss of fat mass (Foreyt et al., 2009, p. S100). Also, high satiety levels may reduce the need for “spontaneous energy intake” in the form of snacks.

Some studies suggest that “low fat diets are more effective for weight maintenance after a period of substantial weight loss” (Foreyt, et al., 2009, p. S101) and even more so when complex carbohydrates are included in this diet. Interestingly, a study into the effect of low carbohydrate diets on energy metabolism concluded that they produce a rapid and more pronounced weight loss than a low-fat diet, mostly so after 3 and 6 months (Erlanson-Albertsson & Mei, 2005, p. S30). However there was “no difference after twelve months between a conventional low-fat diet and the low-carbohydrate diet”.

Low carbohydrate diets are generally low in fibre, calcium, potassium, magnesium, iron, folate and other vitamins (Foreyt et al., 2009, p. S100) however they obviously have a positive affect on insulin sensitivity. The long term safety and efficacy of a low carbohydrate diet is yet to be established.

Therefore, diet-wise, it appears that calorie restriction diets will produce weight loss however the type of calories consumed must be nutrient-dense to maintain general health. Low carbohydrate diets initially produce more weight loss than low fat diets due to increased satiety and water loss through the breakdown of glycogen, however at the twelve month mark they tend to even out. Low fat diets seem to be the most consistent and safe approach to dieting and contribute to sustained weight loss. Other non-dietary factors contributing to obesity and weight loss must be taken into consideration for a successful weight loss plan to work.

References

  • Erlanson-Albertsson, C., Mei, J. (2005). The effect of low carbohydrate on energy metabolism. International Journal of Obesity, 29, S26-S30.
  • Foreyt, J. P., Salas-Salvado, J., Caballero, B., Bullo, M., Gifford, K. D., Bautista, I., Serra-Majem, L. (2009). Weight-reducing diets: Are there any differences? Nutrition Reviews, 67(Suppl. 1), S99-S101.
  • Nordmann, A. J., Nordmann, A., Briel, M. (2006). Effects of low-carbohydrate vs. low-fat diets on weight loss and cardiovascular risk factors: a meta-analysis of randomized controlled trials. Archives of Internal Medicine, 166, 285-293.
  • Whitney, E., Rolfes, S. R. (2008). Appendix H : table of food composition. In Understanding Nutrition (11thed.) (pp.H1-H77). Belmont, Calif: Thompson/Wadsworth.
  • Whitney, E., Rolfes, S. R., Crowe, T., Cameron-Smith, D., Walsh, A. (2012). Understanding Nutrition Australia and New Zealand Edition. South Melbourne: Cengage Learning Australia.