Obesity originates from a failure of the body-weight control systems, which may be affected by changing environmental influences. Basically, the obesity risk depends on two important mutually-interacting factors: (1) genetic variants (single-nucleotide polymorphisms, haplotypes); (2) exposure to environmental risks (diet, physical activity etc.). Common single-nucleotide polymorphisms at candidate genes for obesity may act as effect modifiers for environmental factors. More than 127 candidate genes for obesity have been reported and there is evidence to support the role of twenty-two genes in at least five different populations. Gene–environment interactions imply that the synergy between genotype and environment deviates from either the additive or multiplicative effect (the underlying model needs to be specified to appraise the nature of the interaction). Unravelling the details of these interactions is a complex task. Emphasis should be placed on the accuracy of the assessment methods for both genotype and lifestyle factors. Appropriate study design (sample size) is crucial in avoiding false positives and ensuring that studies have enough power to detect significant interactions, the ideal design being a nested case–control study within a cohort. A growing number of studies are examining the influence of gene–environmental interactions on obesity in either epidemiological observational or intervention studies. Positive evidence has been obtained for genes involved in adiposity, lipid metabolism or energy regulation such as PPARγ2 (Pro12Ala), β-adrenoceptor 2 (Gln27Glu) or uncoupling proteins 1, 2 and 3. Variants on other genes relating to appetite regulation such as melanocortin and leptin receptors have also been investigated. Examples of some recently-identified interactions are discussed.

Physical activity is one of the major non-pharmacological methods for increasing and maintaining bone mineral density (BMD) and geometry. As such, it has an important role in maintaining peak bone mass and strength, thus reducing the risk of future osteoporotic fracture. However, not all exercise is effective, so a prescription in terms of optimal type, intensity, frequency and duration is required. Studies using animal models suggest that loading that is high in magnitude, rapidly applied and novel is most effective, whilst duration is less important beyond a threshold number of cycles. In human subjects cross-sectional studies comparing different athletic populations suggest that those who participate in high- or odd-impact sports have higher BMD; whilst impact exercise, strength training and brief high-impact-jump training interventions increase BMD in premenopausal women. In order to further elucidate exercise recommendations to optimise bone health in this population, the usefulness of brief high-impact unilateral exercises has been evaluated. Brief hopping exercises were shown to be feasible for sedentary premenopausal women, producing ground-reaction forces as high as those from jumping. Regularly performing these hopping exercises over 6 months was found to increase femoral-neck BMD of the trained leg relative to the control leg. Unilateral high-impact exercise may therefore improve bone strength of the trained limb and provide a useful model for comparing exercise prescriptions to help define the most efficient and effective exercise recommendations for the bone health of premenopausal women.

Dietary n-3 PUFA have many beneficial effects on cell and tissue function and on human health. In mammals the n-3 essential fatty acid α-linolenic acid (ALNA) can be converted into longer-chain (LC) n-3 PUFA such as EPA and DHA via a series of desaturase and elongase enzymes that are mainly active in the liver. Human studies have identified that males and females appear to differ in their ability to synthesise EPA and DHA from ALNA, with associated differences in circulating concentrations. Based on studies of women using the contraceptive pill or hormone-replacement therapy and of trans-sexual subjects it is suggested that sex hormones play a role in these differences. The rat has been used to investigate gender differences in n-3 PUFA status since this model allows greater dietary control than is possible in human subjects. Like human subjects, female rats have higher plasma DHA concentrations than males. Rats also respond to increased dietary ALNA in a way that is comparable with available human data. The concentrations of LC n-3 PUFA in rat plasma and tissues are positively associated with circulating concentrations of oestradiol and progesterone and negatively associated with circulating concentrations of testosterone. These findings suggest that sex hormones act to modify plasma and tissue n-3 PUFA content, possibly by altering the expression of desaturase and elongase enzymes in the liver, which is currently under investigation.

Obesity is a global epidemic; increased consumption of energy-dense food and reduced physical activity levels are likely to be the main drivers. Previous cross-sectional research has shown that sedentary males, unlike their active counterparts, are unable to compensate for previous energy intake (EI). Using a longitudinal design a 6-week exercise intervention was found to improve short-term appetite control, leading to a more ‘sensitive’ eating behaviour in response to previous EI, both acutely at a test meal and for the next 24 h. Although the mechanisms whereby acute and chronic exercise improves short-term appetite remain unknown, post-ingestive satiety peptides are likely to be involved. Acute exercise was found to increase postprandial levels of polypeptide YY, glucagon-like peptide-1 and pancreatic polypeptide but to have no impact on ghrelin, suggesting that exercise can trigger physiological changes in satiety hormone secretion that could help in appetite control and weight maintenance. In the context of an increased availability of highly-palatable food, dietary restraint may be increasingly important. Although restraint has been associated with abnormal eating behaviour, in the laboratory no counter-regulation was found in restrained eaters when presented with a buffet meal 60 min after a high-energy preload or when a pasta-meal was presented 3 h after preloading. Although restraint was not found to impact on polypeptide YY or TAG, lower postprandial glucose and insulin plasma levels were observed in restrained eaters, together with increased feelings of fullness. In conclusion, short-term appetite control seems to be favourably modified by exercise, while the impact of restraint on appetite seems to be more complex.

Previous studies have shown that consumption of fruit and vegetables plays a role in preventing the onset of CVD. These beneficial effects have been linked to the presence of polyphenolic compounds in plant-derived foods and their antioxidant capacity. It has been hypothesised that polyphenols may also have a direct effect on vascular endothelial cell growth and the expression of genes involved in angiogenesis and other roles of the endothelium. Previous studies in this area have tended to use concentrations of polyphenols that are supraphysiological (1–100 μm). The effects of more physiological concentrations (0·1 μm) of various individual polyphenols on gene expression were therefore investigated in cultured human umbilical vein endothelial cells (HUVEC) using both microarray and quantitative RT–PCR methodologies. Treatment of HUVEC with ferulic acid, quercetin or resveratrol (0·1 μm) resulted in changes to gene expression that for the three treatments amounted to significant (>2-fold) down-regulation of the expression of 363 genes and significant (>2-fold) up-regulation of 233 genes of the 10 000 genes present on the microarray. The majority of these genes were affected by resveratrol. Quantitative RT–PCR studies indicated that resveratrol (0·1 μm) significantly increased the expression of the gene encoding endothelial NO synthase (eNOS), which synthesises the vasodilator molecule NO, and both resveratrol and quercetin decreased expression of the potent vasoconstrictor, endothelin-1 (ET-1), while ferulic acid had no effect. The effects of resveratrol (0·1 μm) were also investigated when HUVEC were under oxidative stress following treatment with H2O2 (0–50 μm), which dose-dependently increased expression of eNOS and ET-1. Resveratrol stimulated eNOS mRNA in the absence of H2O2 and still allowed the increase with H2O2, but the effects were not additive. In contrast, resveratrol blocked the stimulatory effect of H2O2 on ET-1 expression. Hence, resveratrol has potent effects at a physiological concentration (0·1 μm) that would be expected to result in vasodilation and therefore help reduce blood pressure and the risk of CVD.

Naturally-occurring compounds that have been shown to improve insulin sensitivity include Cr and polyphenols found in cinnamon (Cinnamomon cassia). These compounds also have similar effects on insulin signalling and glucose control. The signs of Cr deficiency are similar to those for the metabolic syndrome and supplemental Cr has been shown to improve all these signs in human subjects. In a double-blind placebo-controlled study it has been demonstrated that glucose, insulin, cholesterol and HbA1c are all improved in patients with type 2 diabetes following Cr supplementation. It has also been shown that cinnamon polyphenols improve insulin sensitivity in in vitro, animal and human studies. Cinnamon reduces mean fasting serum glucose (18–29%), TAG (23–30%), total cholesterol (12–26%) and LDL-cholesterol (7–27%) in subjects with type 2 diabetes after 40 d of daily consumption of 1–6 g cinnamon. Subjects with the metabolic syndrome who consume an aqueous extract of cinnamon have been shown to have improved fasting blood glucose, systolic blood pressure, percentage body fat and increased lean body mass compared with the placebo group. Studies utilizing an aqueous extract of cinnamon, high in type A polyphenols, have also demonstrated improvements in fasting glucose, glucose tolerance and insulin sensitivity in women with insulin resistance associated with the polycystic ovary syndrome. For both supplemental Cr and cinnamon not all studies have reported beneficial effects and the responses are related to the duration of the study, form of Cr or cinnamon used and the extent of obesity and glucose intolerance of the subjects.

Increasing rates of type 2 diabetes (T2DM) follow the obesity ‘epidemic’, with 86% of patients with T2DM being overweight and over half being obese. Literature has highlighted that being overweight or obese increases the risk of diabetes. Weight loss for obese patients is associated with clinical improvements, although this evidence is mostly from short-term studies. As part of a Health Technology Assessment systematic review the long-term (≥2 years) effects of weight loss on change in diabetes-related outcome measures for those with diabetes, or risk of developing diabetes for those without diabetes, was investigated in obese individuals. Eleven studies published between 1966 and 2001 fulfilled the inclusion criteria (Caucasian, BMI >28 kg/m2, adults, no eating disorders, weight loss and changes in diabetes-outcome measures). Results of these studies indicated that intentional weight loss reduces the risk of developing diabetes in the long term and those participants with T2DM often have reduced clinical symptoms and mortality risk. These results have been verified and enhanced by literature published since this review. A similar systematic review was conducted as part of a six-phase project, the PRevent Obesity GRowing Economic Synthesis Study. This review excluded BMI >34 kg/m2 and was restricted to lifestyle interventions (or intentional weight loss). Limited information relating to diabetes was gained, with only a non-significant increasing trend for mortality from diabetes for severe weight cycling practices being suggested. Other results indicated a relationship between weight loss and fasting plasma glucose, but because of the heterogeneity of participation groups and lack of definition in relation to diabetes this relationship was not formalised. In summary, weight loss is beneficial for long-term diabetes outcomes for overweight, obese and morbidly-obese participants. There is little research evidence for those individuals who are overweight or just obese, indicating areas of future research in terms of prevention of both obesity and diabetes.

Complex chemical processes termed non-enzymic glycation that operate in vivo and similar chemical interactions between sugars and proteins that occur during thermal processing of food (known as the Maillard reaction) are one of the interesting examples of a potentially-harmful interaction between nutrition and disease. Non-enzymic glycation comprises a series of reactions between sugars, α-oxoaldehydes and other sugar derivatives and amino groups of amino acids, peptides and proteins leading to the formation of heterogeneous moieties collectively termed advanced glycation end products (AGE). AGE possess a wide range of chemical and biological properties and play a role in diabetes-related pathology as well as in several other diseases. Diabetes is, nevertheless, of particular interest for several reasons: (1) chronic hyperglycaemia provides the substrates for extracellular glycation as well as intracellular glycation; (2) hyperglycaemia-induced oxidative stress accelerates AGE formation in the process of glycoxidation; (3) AGE-modified proteins are subject to rapid intracellular proteolytic degradation releasing free AGE adducts into the circulation where they can bind to several pro-inflammatory receptors, especially receptor of AGE; (4) kidneys, which are principally involved in the excretion of free AGE adducts, might be damaged by diabetic nephropathy, which further enhances AGE toxicity because of diminished AGE clearance. Increased dietary intake of AGE in highly-processed foods may represent an additional exogenous metabolic burden in addition to AGE already present endogenously in subjects with diabetes. Finally, inter-individual genetic and functional variability in genes encoding enzymes and receptors involved in either the formation or the degradation of AGE could have important pathogenic, nutrigenomic and nutrigenetic consequences.

Elevated plasma homocysteine (Hcy) concentrations have been implicated with risk of cognitive impairment and dementia, but it is unclear whether low vitamin B12 or folate status is responsible for cognitive decline. Most studies reporting associations between cognitive function and Hcy or B-vitamins have used a cross-sectional or case–control design and have been unable to exclude the possibility that such associations are a result of the disease rather than being causal. The Hcy hypothesis of dementia has attracted considerable interest, as Hcy can be easily lowered by folic acid and vitamin B12, raising the prospect that B-vitamin supplementation could lower the risk of dementia. While some trials assessing effects on cognitive function have used folic acid alone, vitamin B12 alone or a combination, few trials have included a sufficient number of participants to provide reliable evidence. An individual-patient-data meta-analysis of all randomised trials of the effects on cognitive function and vascular risk of lowering Hcy with B-vitamins will maximise the power to assess the epidemiologically-predicted differences in risk. Among the twelve large randomised Hcy-lowering trials for prevention of vascular disease, data should be available on about 30 000 participants with cognitive function. The principal investigators of such trials have agreed to combine individual-participant data from their trials after their separate publication.

Whereas common infectious and parasitic diseases such as malaria and the HIV/AIDS pandemic remain major unresolved health problems in many developing countries, emerging non-communicable diseases relating to diet and lifestyle have been increasing over the last two decades, thus creating a double burden of disease and impacting negatively on already over-stretched health services in these countries. Prevalence rates for type 2 diabetes mellitus and CVD in sub-Saharan Africa have seen a 10-fold increase in the last 20 years. In the Arab Gulf current prevalence rates are between 25 and 35% for the adult population, whilst evidence of the metabolic syndrome is emerging in children and adolescents. The present review focuses on the concept of the epidemiological and nutritional transition. It looks at historical trends in socio-economic status and lifestyle and trends in nutrition-related non-communicable diseases over the last two decades, particularly in developing countries with rising income levels, as well as the other extreme of poverty, chronic hunger and coping strategies and metabolic adaptations in fetal life that predispose to non-communicable disease risk in later life. The role of preventable environmental risk factors for obesity and the metabolic syndrome in developing countries is emphasized and also these challenges are related to meeting the millennium development goals. The possible implications of these changing trends for human and economic development in poorly-resourced healthcare settings and the implications for nutrition training are also discussed.

UNICEF has stated that urban poverty is primarily found in squatter settlements. At present 13·5% of all South African households live in informal settlements. The major research question is to what extent does poverty influence the food, nutrition and health of informal-settlement dwellers. The purpose of the present study was to determine the depth of poverty in this community and to measure the possible effect that planned food and nutrition interventions may have on eliminating poverty in this area. Pre-tested questionnaires were administered to 340 randomly-selected caregivers. A validated quantified FFQ was administered by trained enumerators as the test measurement for dietary intake and food consumption patterns and 24 h recall was used as the reference measurement, and the data were analysed. A poverty model was used to measure the impact of extra income on the poverty levels of 190 households. Of the respondents 89% lived in Zn shacks and the average household size was 4·9 individuals. The unemployment rate was 94·2% for respondents and 64·9% for their partners. The majority of households (68·8%) had an income of <R 500 (£35) per month and 58·3% spent <R 100 (£6·90) per week on food. The average poverty gap was R 1342·21 (£93) and the poverty gap ratio was 56%. The poverty model showed that an increase of R 500 (£35) in monthly household income results in a poverty gap ratio of 35%. The poverty model confirmed that the impact of food and nutrition interventions on poverty can be measured and that when planning these interventions the model could be used to measure their feasibility. The results indicate that this community is poverty-stricken and has chronic food insecurity, and they will be used to facilitate planning and implementation of sustainable income-generating community-based interventions to promote urban food security and alleviate poverty in this community.

Food insecurity, chronic hunger, starvation and malnutrition continue to affect millions of individuals throughout the developing world, especially Sub-Saharan Africa. Various initiatives by African governments and International Agencies such as the UN, the industrial nations, the International Monetary Fund, the World Bank and the World Trade Organisation to boost economic development, have failed to provide the much-needed solution to these challenges. The impact of these economic shifts and the failures of structural adjustment programmes on the nutritional well-being and health of the most vulnerable members of poor communities cannot be over-emphasised. The use of ad hoc measures as an adjunct to community-based rural integrated projects have provided little success and will be unsustainable unless they are linked to harnessing available local resources. The present paper therefore focuses on exploring alternative ways of harnessing the scant agricultural resources by employing a scientific approach to food-related problem-solving. The food multimix (FMM) concept offers a scientific contribution alongside other attempts currently in use by the World Food Programme, WHO and FAO to meet the food insecurity challenges that confront most of the developing world in the twenty-first century. It is an innovative approach that makes better use of traditional food sources as a tool for meeting community nutritional needs. The FMM concept employs a food-based approach using traditional methods of food preparation and locally-available, cheap and affordable staples (fruits, pulses, vegetables and legumes) in the formulation of nutrient-enriched multimixes. Developed recipes can provide ≥40% of the daily nutritional requirements of vulnerable groups, including patients with HIV/AIDS and children undergoing nutrition rehabilitation. The FMM approach can also be used as a medium- to long-term adjunct to community-based rural integration projects aimed at health improvement and economic empowerment in Sub-Saharan Africa.

Women of child-bearing age (especially pregnant and lactating women), infants and young children are in the most nutritionally-vulnerable stages of the life cycle. Maternal malnutrition is a major predisposing factor for morbidity and mortality among African women. The causes include inadequate food intake, poor nutritional quality of diets, frequent infections and short inter-pregnancy intervals. Evidence for maternal malnutrition is provided by the fact that between 5 and 20% of African women have a low BMI as a result of chronic hunger. Across the continent the prevalence of anaemia ranges from 21 to 80%, with similarly high values for both vitamin A and Zn deficiency levels. Another challenge is the high rates of HIV infection, which compromise maternal nutritional status. The consequences of poor maternal nutritional status are reflected in low pregnancy weight gain and high infant and maternal morbidity and mortality. Suboptimal infant feeding practices, poor quality of complementary foods, frequent infections and micronutrient deficiencies have largely contributed to the high mortality among infants and young children in the region. Feeding children whose mothers are infected with HIV continues to remain an issue requiring urgent attention. There are successful interventions to improve the nutrition of mothers, infants and young children, which will be addressed. Interventions to improve the nutrition of infants and young children, particularly in relation to the improvement of micronutrient intakes of young children, will be discussed. The recent release by WHO of new international growth standards for assessing the growth and nutritional status of children provides the tool for early detection of growth faltering and for appropriate intervention.

HIV/AIDS is associated with biological and social factors that affect the individual's ability to consume and utilize food and to acquire food. These biological and social factors lead to poor nutritional status and weight loss, which are an important cause of morbidity in individuals infected with HIV, resulting in a poor quality of life; weight loss is an important predictor of death from AIDS. The links between nutrition and HIV/AIDS amplify the negative effects of HIV infection on human development at individual, household, community and national levels. For many developing countries the incidence of HIV/AIDS and malnutrition is impeding progress towards achieving the UN millennium development goals. Aggressive interventions to curb the spread of HIV continue to be needed. Concurrent efforts to improve nutrition for populations living with HIV/AIDS should also be given priority.