For decades researcher and nutritionists have been advocating low-fat and low-cholesterol diet. This approach has been touted as a preferred way of losing weight and a way of preventing or controlling heart and other chronic diseases. As a consequence food companies tailored their products to be low in fat, and substituted them with salt, sugar or refined grains to make up for flavor or texture . However, this theory is being given a fresh look. In the 1960s, fats and carbohydrates provide 45% of calories to the Americans adults, and still only 13% of them were obese. Today while Americans eat less fat, yet more of them are obese. Although the role of other factors like lifestyle changes cannot be ruled out. So for rest of the paper, we will be comparing and contrasting low-carb and low-fat diet. We will also be taking into account other factors mentioned earlier.
It has been a common belief over the decades that the more fat one eats the more weight one gains. It is borne out of the presumption that food fat equals body fat, which isn’t completely true. This notion has resulted in lowering fat intake at the cost of increasing carbohydrate intake. It has been observed that the amount of fat in diet isn’t linked to weight or disease. What really matters is the type of fat and the total number of calories in diet. Bad fats such as saturated fats and trans-fat increase the risk of certain diseases. And good fats such as monounsaturated and polyunsaturated fats do just the opposite. The problem switching to low fat diet is that it also prompts people to cut down on fats that are good for heart along with those that aren’t. It also prompts them to replace fats in their diet with easily digestible carbohydrates, such as white bread, white rice, potatoes etc. Other replacements found in fat free diet are sugar and refined carbohydrates. The body digests these carbohydrates very quickly causing blood sugar and insulin level to rise in short period of time. Over long term too much easily digestible carbohydrates raises the risk of heart disease and diabetes equal to or more than saturated fats . That’s why it is important to replace bad fats with good fats, and not carbohydrates.
Other studies have also compared two kinds of weight-loss diets differing in their macronutrient composition that is low-carbohydrate diet versus a low-fat diet. It is easy to presume that under controlled conditions a calorie is a calorie, and its source does not matter. At the same time it is observed that the relation is far more complex in free-living situation. Other factors that condition energy balance must also be taken into consideration. Such factors include total energy intake, satiety and hunger sensory triggers, and palatability should also be taken into consideration while assessing the efficacy of different diet based on their macronutrient composition.
Further, it has been demonstrated that in short-term that a low-fat diet can lead to small weight loss. The same results have been shown with high protein, low-carbohydrate diet. In fact any low-calorie diet in short-term demonstrates such effect. From this we infer that taking into account fat alone, low fat diets offer no additional advantage over diets with fats at national average. This was further demonstrated in the Women’s Health Initiative Dietary Modification Trials. In this trial, women were assigned low-fat diet in the long-term, and they didn’t lose or gain more weight when compared to women eating regular diet . In another study, comparing different weight loss strategies found that low-fat, low-carbohydrate diet were equally effective and equally fast.
According to , because of their higher protein and fat content and lower fibre and carbohydrate content, concerns have been raised about their potential consequences. Short-term studies indicate comparing low-fat and low-carbohydrate found lower levels of triglycerides, higher high-density lipoprotein cholesterol levels and similar low-density lipoprotein levels in person on low-carbohydrate diet. These diets induce greater weight loss at three and six month interval, but the results were not significantly different at one year interval. It needs to be emphasised that weight loss is directly related to calorie content and the ability to maintain its restriction. Low-carbohydrate diets have shown to have lower drop-out rate than low-fat diets because of their high-protein content and low glycemic index, which are known to be hunger suppressing. Data thus far confirm that low-carbohydrate diets are safe and a reasonable alternative to low-fat diet for weight loss.
According to , premenopausal overweight and obese women assigned to follow Atkins diet, which is low in carbohydrate intake, lost more weight and had move favourable overall metabolic effects after 12 months, as compared to Zone, Ornish or LEARN diets. While long-term effects are yet to be determined, a low-carbohydrate, high-protein, high-fat diet may be considered feasible alternative recommendation for weight loss.
Limitations of low-carbohydrate diet have also been expressed. According to , the participant’s weight loss while using low-carbohydrate diets was principally associated with decreased calorie intake and increased diet duration, but now with reduced carbohydrate content. However, lower-carbohydrate diets were not associated with any adverse effects on serum lipid levels, fasting serum glucose levels, or blood pressure. As there are only a few studies have reported on these outcomes, their studies didn’t have statistical power to detect small changes in these measures. Advocates of low-carbohydrate diets claim that higher dietary protein and lower carbohydrate promotes the metabolism of adipose tissue in the absence of dietary carbohydrate and results in rapid weight loss without any significant long term effects. Although, American Diabetes Association and the American Heart Association have cautioned against it use. They feel that low-carbohydrate diet will lead to abnormal metabolic functioning will have serious consequences on those with cardiovascular diseases, type 2 diabetes, dyslipidemia, or hypertension.
A recent study by HSPH tracked the diet and lifestyle of 120,000 men and women for up to 20yrs examining how small changes influenced weight gain over time . It observed that people who ate: nuts, a high fat food; vegetables; whole grains; and fruits gained less weight. In contrast, people who ate: red meat and processed meat, French fries, potatoes, sugary drinks, and refined grains gained weight over the course of years. The study inferred that when people gain calories from nuts, whole grains, fruits and vegetables, they cut down from other refined sources.
It is recommended that one should: eliminate trans-fat from partially hydrogenated oils; limit the intake of saturated fats such as found in red meat and full-fat dairy foods; prefer polyunsaturated fats and monounsaturated fats such as, olive oil, canola oil, sunflower oil etc.; and eat good source of Omega-3 fats every day like fish, walnuts, canola oil, flax seeds oil.
In conclusion, when it comes to losing weight and healthy living, what matters is the kind of fat and the amount calories we consume. Bad fats such as saturated fats and trans-fat increase the risk of certain diseases. And good fats such as monounsaturated and polyunsaturated fats do just the opposite. It needs to be reemphasised that weight loss is directly related to calorie content and the ability to maintain its restriction. Low-carbohydrate diets help to the extent that their high-protein content and low glycemic index are known to be hunger suppressing.
Beresford, S A, K C Johnson and C Ritenbaugh. "Low-fat dietary pattern and risk of colorectal cancer: the Women's Health Initiative Randomized Controlled Dietary Modification Trial." The Journal of the American Medical Association (2006): 643-654. Web. <http://www.ncbi.nlm.nih.gov/pubmed/16467233>.
Bravata, Dena M, et al. "Efficacy and Safety of Low-Carbohydrate Diets : A Systematic Review." The Journal of the American Medical Associaiton (2003): 1837-1850. Web. <http://www.ncbi.nlm.nih.gov/pubmed/12684364>.
Foreyt, J P, et al. "Weight-reducing diets: are there any differences?" Nutr Rev. (2009): 99-101. Web. <http://www.ncbi.nlm.nih.gov/pubmed/19453689>.
Gardner, Christopher D, et al. "Comparison of the Atkins, Zone, Ornish, and LEARN Diets for Change in Weight and Related Risk Factors Among Overweight Premenopausal Women." The Journal of the American Medical Association (2007): 969-977. Web. <http://jama.jamanetwork.com/article.aspx?articleid=205916>.
Hu, Frank B. "Are refined carbohydrates worse than saturated fat?" The American Journal of Clinical Nutrition (2010): 1541-1542. Web. <http://ajcn.nutrition.org/content/91/6/1541.full>.
Last, Allan R and Stephen A Wilson. "Low-Carbohydrate Diets." Am Fam Physician (2006): 1942-1948. Web. <http://www.aafp.org/afp/2006/0601/p1942.html>.
Mozaffarian, Dariush, et al. "Changes in Diet and Lifestyle and Long-Term Weight Gain in Women and Men." The New England Journal of Medicine (2011): 2392 - 2404. Web. <http://www.nejm.org/doi/full/10.1056/NEJMoa1014296>.
Sacks, Frank M, et al. "Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates." The New England Journal of Medicine (2009): 859-873. Web.