Effects Of Dietary Restriction Research Articles

Dietary Restriction: Metabolic Shifting for Cardiac Health

Purpose: To determine the effect of dietary restriction on metabolic pathways and the relationship of the metabolic shifting on antioxidant enzymes in cardiac tissue. Design: Randomized, controlled study. Male rats at 60 days old were randomly divided into four groups. Materials and Methods: The rats of control groups C30 and C60 were given free access to the diet over 30 and 60 days. The rats of the DR30 group were fed 60% of the chow consumed by the control groups over 30 days. The animals of the DR60 group ate 60% of the amount consumed by the C60 group over 60 days. Serum was used for total protein, lactate dehydrogenase (LDH), alanine aminotransferase (ALT) and aspartate aminotransferase (AST). Protein, glycogen, total lipids, superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), LDH, AST and ALT were determined in cardiac tissue. Results: Dietary restriction induced diminished serum and cardiac LDH activities. AST activities were lower in the serum and cardiac muscle of the DR60 animals. Diet...

Effects of dietary restriction on growth, neurobehavior, and reproduction in developing Kunmin mice.

The effects of dietary restriction (DR) on growth, neurobehavior, and reproduction in developing Kunmin mice were investigated in this study. Male and female mice were fed a standard rodent diet ad libitum (control), 80% of control (20% DR), or 65% of control (35% DR) for 3 months. Body weight of DR mice was reduced relative to control except that of females in the 20% DR group (no difference as compared with control group). Learning and memory retention test in a Y maze demonstrated that DR increased learning, but not retention, in male mice, whereas neither learning nor retention was affected in females. The open-field test revealed no difference in exploratory activity in all groups. Reproductive assessment showed that 35% DR retarded the maturation of reproductive function and reduced fertility compared with other groups. Furthermore, both 20% and 35% DR led to a lower level of sperm motility and a higher level of abnormal sperm relative to control mice. These findings indicate that DR does not cause damaging effects on growth and neurobehavior, but imposes a risk to reproductive development events.

Modulations by dietary restriction on antioxidant enzymes and lipid peroxidation in developing mice.

The effects of dietary restriction (DR) on the activities of liver superoxide dismutase (SOD), catalase (Cat), and glutathione peroxidase (GPX) and the level of lipid peroxidation (LP) in developing mice were investigated in this study. Male and female Kunmin mice were fed a standard rodent diet ad libitum (AL), 80% of AL food intake (20% DR), or 65% of AL food intake (35% DR) for 12 or 24 wk. Both 12 and 24 wk of DR resulted in retarded body weight gain in male and female mice. The activities of SOD, Cat, and GPX and the content of LP in DR male and female mice were not different (P > 0.05) from those in controls after 12 wk of DR. However, the SOD activity was increased at 24 wk in 20% DR (P < 0.05) and 35% DR (P < 0.01) male, but not in DR female, mice. The Cat activity was elevated at 24 wk in both DR male (P < 0.05 for 20% DR, P < 0.01 for 35% DR) and female (P < 0.01) mice with a greater increase in DR female (P < 0.05) than in DR male animals. GPX activity was also increased at 24 wk in DR male (P < 0.01) and female (P < 0.01) mice with a greater elevation in DR females (P < 0.05) than in DR males. Furthermore, LP was decreased at 24 wk in both DR male (P < 0.01) and female (P < 0.01) animals with a greater reduction in DR females (P < 0.01) compared with DR males. These findings indicated that 24 wk, but not 12 wk, of DR led to differential effects on liver SOD, Cat, and GPX activities and LP content in male and female mice during development, suggesting sex-associated modulations of DR on antioxidant systems in developing animals.

Effect of dietary restriction beyond middle age: accumulation of altered proteins and protein degradation.

Dietary restriction (DR) from weaning or young adult stages in rodents throughout their usual life span has been shown to prolong longevity and lower or delay (or both) the occurrence of many late-onset diseases, but the effects of DR when performed at middle age or later have not been well investigated. We have studied the effect of DR initiated late in life on altered proteins and protein degradation. DR initiated in 23.5-month-old mice and continued for 2 months reduced the amount of altered proteins and shortened the half-life of proteins, including oxidatively modified ones. Furthermore, our more recent studies in rats demonstrated that DR initiated later in life (26.5 months old) restored the activities of proteasomes that have been implicated in removal of altered proteins. Thus, DR initiated even relatively late in life appears to have beneficial effects, restoring an animal's youthful condition in terms of the age-related accumulation of altered proteins.

Age‐related decline in neurogenesis: Old cells or old environment?

Age‐related decline in neurogenesis: Old cells or old environment?

Effect of Dietary Restriction on Liver Protein Synthesis in Rats

At 6 wk of age, male Fischer F344 rats were fed a purified, casein-based diet either ad libitum or in the amount of 60% of the diet consumed by the rats fed ad libitum (restricted diet). Hepatocytes were isolated from the rats between 2.5 and 19 mo of age. The protein content of the hepatocytes isolated from the rats fed the restricted amount of diet was significantly lower than that of hepatocytes isolated from rats fed ad libitum. The DNA and RNA content of the hepatocytes were similar for the rats fed the two dietary regimens. The absolute rate of protein synthesis for hepatocytes isolated from rats fed ad libitum decreased 55 % between 2.5 and 19 mo of age. However, the rate of protein synthesis by hepatocytes from rats fed the restricted amount of diet decreased only slightly with increasing age. At 19 mo of age, the rate of protein synthesis by hepatocytes from the rats fed the restricted amount of diet was significantly higher than the rate of protein synthesis for hepatocytes from rats fed ad libitum. Therefore, dietary restriction retards the age-related decline in liver protein synthesis. Reproduced by permission. Maria C. Birchenall-Sparks, Michael S. Roberts, Jeffrey Staeker, James E. Hardwick, Arlan Richardson, Effect of Dietary Restriction on Liver Protein Synthesis in Rats. J. Nutr. 115 , 944-950 (1985).

The effect of dietary restriction during development in utero on the frequency of spontaneous somatic mutations.

Caloric or dietary restriction is known to be protective against cancer in humans and in mice but the mechanism is uncertain. Given that somatic mutations are important in carcinogenesis, dietary restriction may act by changing mutation rates. Indeed, previous studies have shown that reductions in caloric intake during development or in adult life make mice less susceptible to high doses of mutagens. In these studies there have been hints that the spontaneous mutant frequency may also be reduced, but no significant decrease has been observed save in one study of very old mice. Since the spontaneous mutant frequency is already low, reductions from this level require the use of much larger sample sizes than usual and larger than those used in the previous studies. As pre-existing mutations cannot be eliminated, it is necessary to reduce the dietary intake over a period of time when a substantial proportion of spontaneous mutations arise in order to see an effect. To overcome such problems, the dietary restriction in this study was applied during the time of the highest mutation rate, early development, and many more than the usual number of animals were studied. SWR female mice were crossed with Muta(TM)Mouse males to obtain F(1) progeny for analysis of mutant frequency. At conception, the dams were put into two groups, one that was fed ad libitum and another which was fed 80% of the ad libitum diet. Pups were killed at birth, DNA was extracted from the whole animal and used to measure the mutant frequencies of the mice at the cII locus. Although the weights of the pups from dams whose diet was restricted were significantly less than those of the ad libitum mice (P = 0.003), the litter sizes in the two groups were approximately the same and did not differ significantly (P = 0.13). There was no significant difference in the mutant frequencies in the dietarily restricted and ad libitum groups (P = 0.43). In addition, there was no significant correlation between the weights of the pups and their mutant frequency in either the ad libitum or dietarily restricted groups (r(2) = 0.14 and r(2) = 0.024). No difference was observed in mutant frequency between the ad libitum and dietarily restricted mice from litters of the same size (P = 0.61). These results indicate that the protective effect of dietary restriction on cancer rates is not mediated by an alteration in the spontaneous rate of mutation but rather by another mechanism, such as its effect on induced mutation.

Effects of diet restriction on life span and age-related changes in dogs.

To evaluate the effects of 25% diet restriction on life span of dogs and on markers of aging. Paired feeding study. 48 Labrador Retrievers. Dogs were paired, and 1 dog in each pair was fed 25% less food than its pair-mate from 8 weeks of age until death. Serum biochemical analyses were performed, body condition was scored, and body composition was measured annually until 12 years of age. Age at onset of chronic disease and median (age when 50% of the dogs were deceased) and maximum (age when 90% of the dogs were deceased) life spans were evaluated. Compared with control dogs, food-restricted dogs weighed less and had lower body fat content and lower serum triglycerides, triiodothyronine, insulin, and glucose concentrations. Median life span was significantly longer for dogs in which food was restricted. The onset of clinical signs of chronic disease generally was delayed for food-restricted dogs. Results suggest that 25% restriction in food intake increased median life span and delayed the onset of signs of chronic disease in these dogs.

Brain evolution and lifespan regulation: conservation of signal transduction pathways that regulate energy metabolism

Mechanisms for sensing, acquiring, storing and using energy are fundamental to the survival of organisms at all levels of the phylogenetic scale. Single-cell organisms evolved surface receptors that sense an energy source and, via signal transduction pathways that couple the receptors to the cell cytoskeleton move towards the energy source. Mutlicellular organisms evolved under conditions that favored species that developed complex mechanisms for obtaining food, with nervous systems being critical mediators of energy acquisition and regulators of energy metabolism. A conserved signaling system involved in regulating cellular and organismal energy metabolism, and in sensing and responding to energy/food-related environmental signals, involves receptors coupled to the phosphatidylinositol-3-kinase–Akt signaling pathway. Prominent activators of this pathway are insulin, insulin-like growth factors and brain-derived neurotrophic factor (BDNF). Recent studies in diverse organisms including nematodes, flies and rodents have provided evidence that insulin-like signaling in the nervous system can control lifespan, perhaps by modulating stress responses and energy metabolism. Interestingly, the lifespan-extending effect of dietary restriction in rodents is associated with increased BDNF signaling in the brain, and a related increase of peripheral insulin sensitivity, suggesting a mechanism whereby the brain can control lifespan. Thus a prominent evolutionarily conserved function of the nervous system is to regulate food acquisition and energy metabolism, thereby controlling lifespan.

Calorific restriction: can we extrapolate from animals to humans?

Dietary restriction in animals results in a dramatic reduction of cancer incidence. Several attempts have been made to extrapolate this observation to the human situation. Recent developments in our knowledge of gene–dietary interactions, particularly in relation to vitamins, have been taken into account in a new examination of the likely effects of dietary restriction in humans, but this is a relatively new area of research. Epidemiological studies in relation to diet have also been considered, but probably need to be refined further because of the subtle effects of dietary interactions. Until more detailed information is available the extrapolation can still only be made with the utmost caution.

Effect of dietary restrictions on growth performance and carcass quality of pigs selected for lean growth efficiency

Sixty-four pigs, 32 selected for lean growth efficiency and 32 controls selected randomly, were used to investigate the effect of genotype and realimentation diets on growth performance and carcass quality of pigs subjected to marginal dietary restrictions during the grower phase. When pigs weighed approximately 20 kg, 16 pens containing two gilts and 16 pens containing two castrated males were randomly assigned within genetic lines to grower diets and finisher diets in a 2×2×2 factorial arrangement of treatments. Grower diets contained 0.421 or 0.765 g lysine/MJ DE, whereas finisher diets contained 0.421 or 0.612 g lysine/MJ DE. Genotype had no effect on growth performance, but select line pigs had better carcass quality ( P≤0.05) and seemed to utilize amino acids more efficiently for growth than control line pigs as indicated by lower blood urea nitrogen ( P≤0.07). During the grower phase, pigs fed the high-amino acid grower diet grew faster and more efficiently ( P<0.01) and had less ultrasound backfat ( P<0.001) than those fed the low-amino acid diet. Although some grower×finisher diet interactions were observed, there was no indication that pigs subjected to early amino acid restrictions exhibited compensatory weight gain, or had different amino acid requirements in the subsequent phase. The rate of lean accretion was similar between pigs fed the low- and high-amino acid grower diets regardless of genotype, indicating that compensatory lean tissue growth may have occurred in pigs subjected to early amino acid restrictions. Furthermore, restricted pigs had better feed efficiency in the subsequent phase, which may have a positive impact on the environment by reducing the excretion of unutilized nutrients. Select line pigs fed the low-amino acid grower diet had lower overall weight gain compared with other groups (genotype×grower, P<0.001). The results imply that pigs selected for lean growth efficiency may be less tolerant of early amino acid restrictions, and offering a grower diet containing adequate amino acids might be important in optimizing overall growth performance.

Effects of dietary restriction on spontaneous dermatitis in NC/Nga mice.

In laboratory animals, dietary restriction prolongs life span, improves physiologic function, and prevents or lessens severity of several diseases including some experimental inflammatory states. We investigated the effect of dietary restriction on a spontaneously occurring mouse model of atopic dermatitis, an inflammatory skin disease. NC/Nga mice were assigned to a group fed ad libitum or to a restricted diet group receiving 60% of the amount of food consumed by the other group. Dermatitis was characterized according to extent, intensity, and scratching time. We then used computer-assisted image analysis to quantify immunologic findings in skin sections. Extent, intensity score, and scratching time in mice with restriction increased more gradually than in mice fed ad libitum. Infiltrating inflammatory cells (CD4-positive T cells, CD8-positive T cells, eosinophils, and mast cells) as well as interleukin-4 and -5 secreted into tissue were reduced in mice with restriction. In conclusion, dietary restriction delayed onset and progression of spontaneous dermatitis in NC/Nga mice, an effect possibly involving inhibition of inflammatory infiltration cell and cytokine secretion.

Dietary Restriction in Mice Beginning at One Year of Age: Effect on Life-Span and Spontaneous Cancer Incidence

Lifelong dietary restriction beginning at 3 to 6 weeks of age in rodents is known to decelerate the rate of aging, increase mean and maximum life-spans, and inhibit the occurrence of many spontaneous cancers. Little is known about the effects of dietary restriction started in middle age. In the experiments now reported, the food intake of 12- to 13-month-old mice of two long-lived strains was restricted by using nutrient-enriched diets in accordance with the concept of “undernutrition without malnutrition.” The mice on the restricted diet averaged 10 to 20% increases in mean and maximum survival times as compared with the control mice. Spontaneous lymphoma was inhibited by the food restriction. Reproduced with permission from Science . Copyright 1982 American Association for the Advancement of Science. Richard Weindruch, Roy L. Walford, Dietary Restriction in Mice Beginning at One Year of Age: Effect on Life-Span and Spontaneous Cancer Incidence. Science 215 , 1415-1418 (1982).

Endocrine Effects of Dietary Restriction and Aging: The National Institute on Aging Study

Calorie restriction (CR) has been shown repeatedly to extend lifespan and reduce the incidence of age-related disease in a variety of animal models. Rhesus monkeys experience many age-related changes in hormone function that parallel those observed in humans and evidence suggests that CR is a safe and effective means for slowing many of these aging changes. In the National Institute on Aging (NIA) long-term study on rhesus monkeys, CR improved glucoregulatory function and disrupted both the thyroid and growth hormone axis, all of which may be important for mediating the effects of CR. Male monkeys experienced delayed puberty. However, data from old females indicated that restriction did not alter hormone levels or cycling—thus, reducing the potential risk of reproductive dysfunction due to lower caloric intake. While it is certainly advantageous to document improved health and longevity, the long lifespan of nonhuman primates dictates the need to develop physiological biomarkers of aging. Dehydroepiandros...

Modulation by dietary restriction in gene expression related to insulin-like growth factor-1 in rat muscle.

Physiological adaptations induced by dietary restriction might include the modulation of the insulin-like growth factor 1 (IGF-1) axis. We investigated the effects of dietary restriction on aging-dependent changes in plasma level of IGF-1 and gene expression levels of type-1 IGF receptor (IGFR), insulin receptor substrate-1 (IRS-1), and IGF-1 in the diaphragm and quadriceps femoris muscle (QFM) of male F344 rats. The animals were fed ad libitum throughout life (AL), or provided with 70% of diet of AL rats from 6 weeks of age (DR). The plasma IGF-1 and steady-state levels of the genes were quantified by radioimmunoassay and the reverse transcription-polymerase chain reaction method, respectively. Immunohistochemical analysis in tissue sections was also performed for IGFR. Our results showed that dietary restriction: 1) decreased the plasma level of IGF-1; 2) increased the steady-state level of IGFR-mRNA at 6 and 16 months of age. and the peptide level at 6 months; 3) maintained IGF-1- and IRS-1-mRNA at a level similar to that in AL rats; and 4) delayed or inhibited an aging-dependent increase in IGFR-mRNA in the muscles. The present results suggest that dietary restriction could modulate IGF-1 signaling by augmenting local tissue response to IGF-1 and by maintaining the local production of the peptide, even though plasma IGF-1 is reduced.

Effect of dietary restriction on age-related increase of liver susceptibility to peroxidation in rats.

Dietary restriction (DR) increases life span and decreases age-related diseases in experimental animals. It has received a great deal of attention in connection with the relationship between aging, nutrition, and oxidative stress because oxidative injury in several organ systems is a prominent feature in aging. We investigated the possibility that DR can protect vulnerable liver lipids against age-related increases of peroxidation. Male Fischer 344 rats fed ad libitum (AL) or dietarily restricted (maintained on 60% of AL food intake) were killed by decapitation at 4 (young) or 12 mon (adult) of age. Phosphatidylcholine hydroperoxide (PCOOH) concentration of liver was determined using a chemiluminescent high-performance liquid chromatographic method. Liver PCOOH increased with age in adult rats, but less of an increase of PCOOH was seen in DR rats, which is consistent with results on production of thiobarbituric acid-reactive substances and oxygen-derived free radicals. No significant differences were found in liver superoxide dismutase and catalase activity between AL and DR groups of young and adult rats. Liver triglyceride and cholesterol contents were lower in DR than AL rats at 12 mon. Fatty acid compositions of phosphatidylcholine and phosphatidylethanolamine indicated that the ratio of (20:3n-6 + 20:4n-6)/18:2n-6, an index of linoleic acid (18:2n-6) desaturation, was lower in DR than in AL rats. We concluded that DR suppresses age-related oxidative damage in liver by modulating the amount of lipid as well as fatty acid composition.

Age-related changes in oxidative damage to lipids and DNA in rat skin

Skin is a tissue exposed most frequently to oxidative stress from the environment in daily life. Age-related changes of oxidative damage and antioxidant enzyme activity in the skin were examined in male Fischer 344 rats aged 6 to 30 months. The contents of phosphatidylcholine hydroperoxide (PCOOH) and thiobarbituric acid-reacting substances (TBARS) increased linearly with age. The content of cholesterol hydroperoxide increased until 24 months of age and then decreased. The content of 8-oxo-2′-deoxyguanosine (8-oxodG) increased gradually with age, and was significantly higher at 30 months of age than at 6 months of age. Superoxide dismutase activity tended to decrease with age. The activities of catalase and glutathione peroxidase showed no changes with age. We examined the effect of dietary restriction on the accumulation of oxidative damage in rat skin. The increase in PCOOH content in the skin of dietary-restricted rats was suppressed until 30 months of age. The TBARS and cholesterol hydroperoxide contents in the skin of dietary-restricted rats were significantly lower than in the skin of ad libitum-fed rats, while the 8-oxodG content was somewhat lower in the dietary-restricted rats than the ad libitum-fed rats. These results indicate that oxidative damage to the lipids and DNA in rat skin increases with age and that dietary restriction delays the accumulation of oxidative damage in skin.

Caloric restriction mimetics: physical activity and body composition changes.

As the only paradigm that has consistently increased life span and inhibited the onset and/or progression of disease, dietary restriction has multiple effects on a variety of organ systems. In this brief review, the goal of the panel was to attempt to understand the role of changes in physical activity and body composition as possible modulators of the life span in experimental animals and humans. We focus on whether changes in exercise behavior and body composition produce similar changes as those found in dietary restriction and whether these changes can be used to either replace or enhance the beneficial effects of dietary restriction. The complexity of the two stimuli is emphasized in our report, with suggestions offered on how to better interpret existing research. Our panel briefly examines evidence in experimental animals and humans about the specific contributions of each of these factors to altering life span and age-related pathologies. We also discuss additional animal studies and/or human intervention studies that could be performed to clarify these issues. Finally, we provide suggested avenues for future research in this area of changes in physical activity and body composition as dietary restriction mimetics.

Skeletal muscle and aging.

Age-related changes in muscle mass (sarcopenia) and functional properties are the result of a very complex hierarchical system of basic cell aging processes and cell adaptive responses. A basic aging mechanism pertains to mitochondrial production of free radicals and their associated secondary effects. From this basic aging mechanism many other cellular changes can be explained as direct effects or compensatory changes. Altered skeletal muscle cell biochemical and functional properties during aging resulting from intrinsic mechanisms and from changes in hormonal or local signals that influence phenotype maintenance, are reviewed. The effect of skeletal muscle cell senescence on the cellular response to exercise, and the effect of dietary restriction on muscle cell senescence can also be explored from this perspective.

The suppressive effect of dietary restriction and weight loss in the obese on the generation of reactive oxygen species by leukocytes, lipid peroxidation, and protein carbonylation.

Increased reactive oxygen species generation by the leukocytes of the obese may be responsible for increased oxidative injury to lipids and proteins and, hence, atherosclerosis. We have investigated whether reactive oxygen species generation by leukocytes and other indexes of oxidative damage in the body fall with short-term dietary restriction and weight loss. Nine nondiabetic obese subjects (body mass index, 32.5-64.4 kg/m(2)), not taking any antioxidants, were put on a 1000-Cal diet. Fasting blood samples were taken at 0, 1, 2, 3, and 4 weeks and at 12 weeks after the cessation of dietary restriction. Blood samples were also obtained at 1 and 2 h after administration of 75 g oral glucose at 0 and 4 weeks. Mononuclear cells (MNC) and polymorphonuclear leukocytes (PMN) were isolated, and reactive oxygen species generation was measured. Plasma concentrations of thiobarbituric acid-reactive species (TBARS), 13-hydroxyoctadecadienoic acid (13-HODE), 9-hydroxyoctadecadienoic acid (9-HODE), carbonylated proteins, o-tyrosine, and m-tyrosine as indexes of oxidative damage to lipids, proteins and amino acids, respectively, were measured. Antioxidant vitamins were measured as indexes of antioxidant reserves. Plasma tumor necrosis factor-alpha concentrations were also measured. Mean weight loss was 2.4 +/- 0.6 kg at week 1, 2.5 +/- 1.7 kg at week 2, 3.9 +/- 0.8 kg at week 3, and 4.5 +/- 2.8 kg at week 4 (P < 0.05). Reactive oxygen species generation by PMN fell from 236.4 +/- 95.8 to 150.9 +/- 69.0, 125.9 +/- 24.3, 96.0 +/- 39.9, and 103.1 +/- 35.7 mV at weeks 1, 2, 3, and 4, respectively (P < 0.001). It increased 3 months after the cessation of dietary restriction to 270.0 +/- 274.3 mV. Reactive oxygen species generation by MNC fell from 187.8 +/- 75.0 to 101.7 +/- 64.5, 86.9 +/- 42.8, 63.8 +/- 14.3, and 75.1 +/- 32.2 mV and increased thereafter to 302.0 +/- 175.5 mV at 1, 2, 3, 4, and 16 weeks, respectively (P < 0.005). Reactive oxygen species generation by PMN and MNC increased in response to glucose; the relative increase was greater at 4 weeks than that at week 0 due to a fall in the basal levels of reactive oxygen species generation. Consistent with the fall in reactive oxygen species generation, there was a reduction in plasma TBARS from 1.68 +/- 0.17 micromol/L at week 0 to 1.47 micromol/L at 4 weeks (P < 0.05). The 13-HODE to linoleic acid ratio fell from a baseline of 100% to 56.4 +/- 36.1% at 4 weeks (P < 0.05), and the 9-HODE to linoleic acid ratio fell from a baseline of 100% to 60.5 +/- 37.7% at 4 weeks (P < 0.05). Carbonylated proteins fell from 1.39 +/- 0.27 microgram/mg protein at week 0 to 1.17 +/- 0.12 microgram/mg protein at week 4 (P < 0.05); o-tyrosine fell from 0.42 +/- 0.03 mmol/mol phenylalanine at week 0 to 0.36 +/- 0.02 mmol/mol phenylalanine at 4 weeks (P < 0.005), and m-tyrosine fell from 0.45 +/- 0.04 mmol/mol phenylalanine at week 0 to 0.40 +/- 0.03 mmol/mol phenylalanine at 4 weeks (P < 0.05). The basal concentrations of TBARS, 9-HODE, 13-HODE, carbonylated proteins, o-tyrosine, and m-tyrosine in the obese were significantly greater than those in normal subjects. On the other hand, tumor necrosis factor-alpha concentrations did not change during this 4-week period, nor was there any change in antioxidant vitamins. This is the first demonstration of 1) an increase in reactive oxygen species-induced damage in lipids, proteins, and amino acids in the obese compared with normal subjects; and 2) a decrease in reactive oxygen species generation by leukocytes and oxidative damage to lipids, proteins, and amino acids after dietary restriction and weight loss in the obese over a short period.