‘Crash’ diets often prescribed for quick weight loss are usually unbalanced and lead to health issues that can be dangerous in the long run, a new review of popular diets published in Indian Journal of Medical Research has warned.
Researchers classified extreme diets into low-carbohydrate (less than 100 grams per day) and high-fat ( over 60%) such as Atkins’s Diet and Protein Power Lifeplan; low-fat (11-19 %) such as the Dean Ornish Diet (basically a vegetarian diet) and the Pritikin diets (limited quantities of low-fat animal protein); and the very-low-fat ( less than 10 %) diet. They then analyzed reasons behind weight loss across various popular diets and their effects on the body. The analysis has been done by Dr Viswanathan Mohan (Madras Diabetes Research Foundation) and Dr Shilpa Joshi (Mumbai Diet & Health Centre).
Weight loss that occurs due to restriction in carbohydrates in ‘low-carbohydrate/high-fat’ diet in the early stages is due to water loss. Thereafter, weight loss is due to lesser intake of carbohydrates rather than fat being used up, as is popularly believed. This is because even though the individual is allowed to eat fats the actual consumption is not as much. One of the reasons could be that one cannot consciously consume too much dairy fat and most Indians take more vegetarian food on a daily basis than eggs or meat. Only a marginal increase of protein intake takes place. The energy deficit as a result of lesser intake of carbohydrates and fats actually causes weight loss.
Low-carbohydrate/high-fat diets taken over a period of time may cause the body’s immunity system to malfunction and cause damage to various organs. As low-carbohydrate diets encourage low intake of fruits, vegetables and dietary fibre, it may increase risk of intestinal cancers. Very high protein intake makes bones weak as calcium gets removed via urine thereby making it unavailable to bones.
Low-fat diets are also usually by default high-carbohydrate diets and include vegetables, fruits, whole grains and beans, egg white, non-fat dairy, soya and white flour. They decrease bad cholesterol during early stages but eventually lead to an increase in stored fat (triglyceride levels) if the diet contains more than 70 per cent carbohydrates. However, if sufficient fibre is included cholesterol levels and blood pressure may decrease, leading to reduction in antihypertensive medications. These diets also usually decrease blood glucose and insulin levels thus benefitting diabetics.
"Weight loss that occurs due to restriction in carbohydrates in ‘low-carbohydrate/high-fat’ diet in the early stages is due to water loss. "
The study recommends a short-term ‘very low carbohydrate diet’ (less than 800 kcals per day or 80 grams carbohydrate and 15 grams fat per day) to induce weight loss and to achieve a favourable metabolic profile. Lean body mass is preserved by providing adequate dietary protein in the form of milk, soy or egg-based powder which is mixed with water and consumed as a liquid. Recommended daily allowance (RDA) of essential vitamins and minerals is also ensured. The source of protein may be from lean meat, fish and poultry. These diets must be supplemented with a multivitamin and 2 to3 grams per day potassium and adequate fluid intake.
However, very low carbohydrate diets are also associated with risk of gallstones, muscle loss, fatigue and increase in uric acid levels causing painful joints. Long-term safety data of these diets and whether these diets cause any micronutrient deficiency also needs to be established, the study said.
The Prospective Urban and Rural Epidemiological (PURE) Study had also concluded that high carbohydrate diet had a higher death rate, possibly due to increased availability of blood sugar which increases obesity and the risk of acquiring diabetes. A very-low-carbohydrate diet also markedly increases the death rate due to low blood sugar causing loss of energy and can have serious consequences, if left untreated.
The study concludes that maintaining negative energy balance deficit of 500-1000 kcals per day is essential for weight loss. As this is very difficult to attain and sustain on a regular basis, the ‘drop out’ rate is also high. It proposes that a balanced and tasty diet which could lead to weight loss should have lesser calorie intake, moderate carbohydrate (40 - 50%) and fat (30%) diets with healthy monounsaturated fats and adequate protein (20-25 %) along with plenty of green leafy vegetables. The study also suggests individualized programmes while advocating a wide range of food choices (including supplements) for variety, a physical exercise regimen to consume the energy and continuous counselling to ensure that once weight loss is achieved it is maintained rather than ‘crash diets’ to tackle the obesity epidemic in India.
Ms. Anuja Agarwala, senior dietitian from the All India Institute of Medical Sciences, who was not associated with the review, said “the study is important because it addresses the real issue of the lack of consensus amongst professionals in advising weight loss diets and confusion among the common man as to which diet they should follow.” She said a standard protocol was needed based on a well-designed long-term study on many Indians to establish benefits of the diet prescribed in the study.
India Science Wire