Various health benefits are being offset by global shifts to unhealthy diets that are high in calories and heavily-processed and animal source foods, according to a recent report released by the Lancet Commission.
The trends of unhealthy diets are driven partly by rapid urbanisation, increasing incomes and inadequate accessibility of nutritious foods, it added.
Concurrently, the prevalence of diseases, associated with high-calorie and unhealthy diets, is increasing with 2.1 billion adults overweight or obese and the global prevalence of diabetes almost doubled in the past 30 years.
Unhealthy diets are the largest global burden of disease and pose a greater risk to morbidity and mortality than does unsafe sex, alcohol, drug and tobacco use combined.
As much of the global population is inadequately nourished (i.e. undernutrition, over-nutrition and malnutrition), the world's diets urgently need to be transformed.
The commission expressed concern that current dietary trends, combined with projected population growth to about 10 billion by 2050, will exacerbate risks to people and planet.
The global burden of non-communicable diseases is predicted to worsen and the effects of food production on greenhouse gas emissions, nitrogen and phosphorus pollution, biodiversity loss, and water and land use will reduce the stability of the Earth system.
The report said transitions to unhealthy diets are not only increasing the burden of obesity and diet-related non-communicable diseases, but are also contributing to environmental degradation.
Low dietary quality contributes to undernutrition, overweight, and obesity, and has caused persistent micronutrient deficiencies. Globally, more than 820 million people remain undernourished, 151 million children are stunted, 51 million children are wasted, and more than 2.0 billion people are micronutrient deficient.
Most studies investigating the effects of climate change on food production indicate an aggregate reduction in future agricultural productivity by 8.0 per cent in mean yield of all crops by 2050 across Africa and south Asia.
For major crops (wheat, rice, and maize) in tropical and temperate regions, local temperature rises by 2°C or more without adaptation will negatively affect production. However, substantial variability exists between regions, crops and adaptation scenarios.
About 10 per cent of projections for 2030-49 showed more than 10 per cent increase in food production whereas about 10 per cent of projections showed more than 25 per cent decrease, with risks of more severe effects increasing after 2050.
Climate change will also affect fisheries and aquaculture. Increased productivity is estimated at high latitudes and decreased productivity at low and mid latitudes, with considerable regional variation. For example, pole-ward migration of fish alone has been estimated to reduce maximum catch potential in some tropical areas by up to 40 per cent.
However, deviation from current yields rarely exceeds 10 per cent.
The effects of climate change on agriculture are expected to substantially impact human health. Reductions in agricultural production due to climate change have been estimated to cause 500,000 climate-related deaths in 2050, most of which are due to reduced fruit and vegetable production and consumption, followed by increases in underweight from reduced availability of food.
Developing crop varieties that can withstand heat, drought, flood, and other extreme weather events might be most important step to adapt to climate change.
Transformation to healthy diets by 2050 will require substantial dietary shifts, including a greater than 50 per cent reduction in global consumption of unhealthy foods, such as red meat and sugar, and a greater than 100 per cent increase in consumption of healthy foods, such as nuts, fruits, vegetables and legumes. However, the changes needed differ greatly by region.
Dietary changes from current diets to healthy diets are likely to substantially benefit human health, averting about 10.8-11.6 million deaths per year, a reduction of 19.0-23.6 per cent.
Transformation to healthy diets from sustainable food systems is necessary to achieve the UN Sustainable Development Goals and the Paris Agreement, and scientific targets for healthy diets and sustainable food production are needed to guide a Great Food Transformation.
Transformation to sustainable food production by 2050 will require at least a 75 per cent reduction of yield gaps, global redistribution of nitrogen and phosphorus fertiliser use, recycling of phosphorus, radical improvements in efficiency of fertiliser and water use, rapid implementation of agricultural mitigation options to reduce greenhouse gas emissions, adoption of land management practices that shift agriculture from a carbon source to sink and a fundamental shift in production priorities.
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