A seaweed extract could be used to produce healthy burgers, pies and cakes that taste just as good as the full-fat varieties, scientists said yesterday.Alginates could replace the fats in many junk foods, increasing their fibre content while adding the moisture that gives them an appealing texture.Scientists at Newcastle University said substituting alginates for unhealthy fats could prove valuable in the battle against obesity, diabetes, heart problems and diseases such as bowel cancer. Alginate, which is high in fibre, is already in widespread use by the food industry as a gelling agent and to thicken the frothy head of premium lagers.