Comparison of Weight-Loss Diets with Different Compositions of Fat, Protein, and Carbohydrates

Department of Nutrition, Harvard School of Public Health, Boston, USA.
New England Journal of Medicine (Impact Factor: 55.87). 02/2009; 360(9):859-73. DOI: 10.1056/NEJMoa0804748
Source: PubMed


background The possible advantage for weight loss of a diet that emphasizes protein, fat, or carbohydrates has not been established, and there are few studies that extend beyond 1 year. methods We randomly assigned 811 overweight adults to one of four diets; the targeted percentages of energy derived from fat, protein, and carbohydrates in the four diets were 20, 15, and 65%; 20, 25, and 55%; 40, 15, and 45%; and 40, 25, and 35%. The diets consisted of similar foods and met guidelines for cardiovascular health. The participants were offered group and individual instructional sessions for 2 years. The primary outcome was the change in body weight after 2 years in two-by-two factorial comparisons of low fat versus high fat and average protein versus high protein and in the comparison of highest and lowest carbohydrate content. results At 6 months, participants assigned to each diet had lost an average of 6 kg, which represented 7% of their initial weight; they began to regain weight after 12 months. By 2 years, weight loss remained similar in those who were assigned to a diet with 15% protein and those assigned to a diet with 25% protein (3.0 and 3.6 kg, respectively); in those assigned to a diet with 20% fat and those assigned to a diet with 40% fat (3.3 kg for both groups); and in those assigned to a diet with 65% carbohydrates and those assigned to a diet with 35% carbohydrates (2.9 and 3.4 kg, respectively) (P>0.20 for all comparisons). Among the 80% of participants who completed the trial, the average weight loss was 4 kg; 14 to 15% of the participants had a reduction of at least 10% of their initial body weight. Satiety, hunger, satisfaction with the diet, and attendance at group sessions were similar for all diets; attendance was strongly associated with weight loss (0.2 kg per session attended). The diets improved lipid-related risk factors and fasting insulin levels.

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    • "Furthermore, increasing dietary protein can help maintain SkM mass during periods of disuse (reviewed in Wall & van Loon, 2013) and induce greater increases in skeletal muscle hypertrophy following chronic supplementation when combined with exercise (resistance) vs. exercise alone (meta-analysis Cermak et al., 2012). Indeed, there is substantial support to suggest that with DR, overall weight loss is no different with higher protein intakes vs. DR alone (Sacks et al., 2009; de Souza et al., 2012). With some acute trials showing that fat mass decreases while SkM is spared (Krieger et al., 2006), importantly, exercise in combination with higher protein content in DR diets seems to have a SkM maintaining effect (Garthe et al., 2011; Josse et al., 2011; Mojtahedi et al., 2011), without negative impact on markers of mitochondrial biogenesis, albeit after acute fasting in humans (Taylor et al., 2013). "
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    ABSTRACT: Advancing age is associated with a progressive loss of skeletal muscle (SkM) mass and function. Given the worldwide aging demographics, this is a major contributor to morbidity, escalating socio-economic costs and ultimately mortality. Previously, it has been established that a decrease in regenerative capacity in addition to SkM loss with age coincides with suppression of insulin/insulin-like growth factor signalling pathways. However, genetic or pharmacological modulations of these highly conserved pathways have been observed to significantly enhance life and healthspan in various species, including mammals. This therefore provides a controversial paradigm in which reduced regenerative capacity of skeletal muscle tissue with age potentially promotes longevity of the organism. This paradox will be assessed and considered in the light of the following: (i) the genetic knockout, overexpression and pharmacological models that induce lifespan extension (e.g. IRS-1/s6K KO, mTOR inhibition) versus the important role of these signalling pathways in SkM growth and adaptation; (ii) the role of the sirtuins (SIRTs) in longevity versus their emerging role in SkM regeneration and survival under catabolic stress; (iii) the role of dietary restriction and its impact on longevity versus skeletal muscle mass regulation; (iv) the crosstalk between cellular energy metabolism (AMPK/TSC2/SIRT1) and survival (FOXO) versus growth and repair of SkM (e.g. AMPK vs. mTOR); and (v) the impact of protein feeding in combination with dietary restriction will be discussed as a potential intervention to maintain SkM mass while increasing longevity and enabling healthy aging. © 2015 The Authors. Aging Cell published by the Anatomical Society and John Wiley & Sons Ltd.
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    • "Pre - ordering programs have been created with the assumption that ordering food in advance of meal - time may mit - igate hunger - based , impulsive selections and eliminate sensory cues that lead to less healthy choices ( Hanks , Just , Smith , Wansink , & Dyson , 2012 ) . An earlier commitment to a more beneficial , future outcome ( such as weight loss ) can prevent someone from suc - cumbing to a temptation in the immediate environment ( such as unhealthy lunch choices ) ( Rachlin , 2009 ) . Precommitment is about acting in the present to make a better future . "
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    • "It has been suggested that providing dietary choice may increase weight loss because participants will choose diets that align with their food preferences, which may result in greater adherence to the diet (Sacks et al., 2009; Samaha et al., 2003). The current study supports the first part of the assertion; that is, most participants chose a diet approach that was consistent with their food preferences as measured by a valid and reliable macronutrient preference questionnaire. "
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