N° 9 | February 2007

Role for fruit content in low energy diets

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Classically, energy-restricted diets have included fruits as lowcalorie fuel. However, depending on fruit type, carbohydrate and fiber composition as well as other components vary, and should be also taken into account as these differences may influence antioxidant power, glycemic index and energy content.

Balanced low-energy diet and weight management

The prescription of nutritionally equilibrated low-energy diets is a common strategy for body-weight reduction. These diets are designed according to traditional nutrient recommendations to supply a balanced ratio of protein (10-20% energy), carbohydrate (50-65% energy), and fat (25-35% energy) in reduced quantities to provide an energy intake of 3350-6280 KJ (800-1500 kcal/d). However, traditional nutritionally adequate low-energy diets have frequently failed to promote stable weight loss, and the explanations for such limited success have been attributed to “poor adherence” to specific low-energy diets. Thus, dietary approaches based upon changes in the macronutrient distribution rather than food restriction to treat overweight are becoming increasingly popular because they might favourably affect weight loss and lipid profile1. Consequently, at the present time, clinical trials showing that the enrichment of diets with foods that have antioxidant properties such as fruits with the purpose of reducing the risk of illnesses associated to the obesity like atherosclerosis and diabetes, among others2 could provide additional value for health.

Fruit and body weight loss

Fruit contains a high amount of fructose, a secondary carbohydrate in supplying energy. Thus, fruit intake could conceivably induce body weight gain. However, moderate fructose intake with a low glycemic index does not adversely affect body composition. This monosaccharide does not require insulin for uptake into cells and moderate fructose intake appears less likely to cause symptoms of reactive hypoglycemia, or to trigger hypoglycemia-related overeating. For these reasons, fructose is often included in many weightloss products.

However this view concerning the healthy benefits of fructose is being currently challenged. Regarding this fact, one clinical trial included obese women who follow two hypocaloric diets with different fruit content. Results showed that the consumption of a high-fruit energy-restricted diet for 8 weeks involved no remarkable benefits or deleterious effects related to weight loss and general metabolic indicators as compared to a low-fruit hypocaloric diet3. These outcomes could be explained as effect of the energy restriction and also because the increased intake fructose is associated to higher fiber content3.

Fruit and antioxidant protection during weight loss

Increased reactive oxygen species generation has been described in the obese and may result in oxidative injury to cell lipids and proteins that may be associated with comorbidities in the obese. Cells contain a variety of antioxidant compounds, such as uric acid, bilirubin, ascorbic acid and vitamin E, which provide protection against oxidative stress. The major source of these antioxidants is the diet, although weight loss in obese individuals has been also hypothesized to reduce oxidative stress. So, caloric restriction diets including antioxidants-enriched foods could be a doubly effective strategy to inhibit oxidative injuries4.

Fruits are often considered a healthy food because they contain a variety of compounds with antioxidant capacity, such as vitamins C and E, carotenoids, flavonoids, and polyphenols which may have beneficial actions. The protective effect of fruit may be related to a decrease in free radical production or stimulation of other antioxidative processes. In this context, obese women consuming a highfruit hypocaloric diet showed a higher decrease in total cholesterol levels and higher increase in antioxidant capacity than obese women who consumed low-fruit hypocaloric diet specifically due to fiber and fructose content of fruit, while the weight loss was similar in both dieting groups4.

In conclusion, daily intake of fruit that provides fructose, fiber, and different bioactive compounds that may have specific effects on weight management and oxidant status. The supply of fiber and antioxidant substances naturally occurring in fruits could be a useful strategy in the design of hypocaloric diets that, with body weight reduction, could produce an improvement in cardiovascular risk factors related to obesity.

  1. Abete I, Parra MD, Zulet MA, Martínez JA. Different dietary strategies for weight loss in obesity: role of energy and macronutrient content. Nutr Res Rev. 2006;19:1-19.
  2. Djuric Z, Uhley VE, Naegeli L, Lababidi S, Macha S, Heilbrun LK. Plasma carotenoids, tocopherols, and antioxidant capacity in a 12-week intervention study to reduce fat and/or energy intakes. Nutrition. 2003;19:244-9.
  3. Rodriguez MC, Parra MD, Marques-Lopes I, De Morentin BE, Gonzalez A, Martinez JA. Effects of two energy-restricted diets containing different fruit amounts on body weight loss and macronutrient oxidation. Plant Foods Hum Nutr. 2005;60:219-24.
  4. Crujeiras AB, Parra MD, Rodriguez MC, Martinez de Morentin BE, Martinez JA. A role for fruit content in energy-restricted diets in improving antioxidant status in obese women during weight loss. Nutrition. 2006;22:593-9.
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