There are various ways to check whether your weight is appropriate.(1)
Body Mass Index (BMI) assesses weight relative to height and it is calculated by dividing weight in kilograms by (height in metres.)2
BMI= weight (kg)
The calculation can also be made using imperial units by multiplying the weight in pounds by 703, then dividing by the (height in inches.)2
BMI= weight (lb) x703
The World Health Organization recommends a BMI for adults of between 18.5 and 25.(2)
Those with higher BMIs generally have higher percentages of body fat,(3) but BMI does not take into account aspects of body composition which are important for health outcomes.(4) Some people, who are very muscular, such as athletes, may have a high BMI without having excess body fat. Similarly, some people may have very high levels of body fat, but not be identified as obese by a BMI calculation.(5)
One way to tell whether it is advisable for you to lose weight is to calculate your waist-to-hip ratio. Higher waist-to-hip ratios indicate higher levels of abdominal fat. Fat located around the middle is more harmful to health than fat carried on the hips and thighs.(6) You can calculate your waist-to-hip ratio by dividing your waist measurement by your hip measurement. Ideally, for women, the resulting figure should be less than 0.85 and for men, it should be less than 1.0. A higher number indicates that you are carrying too much weight around your middle and are at an increased risk of diseases that are linked to obesity, such as type-2 diabetes and heart disease.(7)
If you believe that your weight is at an unhealthily low or high level, it is sensible to confirm this with your doctor before you embark on a programme of weight loss or weight gain.
If you need to lose weight
Genetic and environmental factors may contribute to weight gain(8) (9) but at an individual level, changes in weight are due to calorie imbalance. In order to lose weight, you will need to consume fewer calories than your body burns. This calorie deficit can be produced by both diet and exercise.(10) The amount of exercise necessary for weight loss and weight maintenance depends on the individual and on their diet. Increased exercise may not be sufficient in itself to meet your weight loss goals.
Diet is also crucial. You should avoid those foods and drinks which are low in nutritional value, but high in calories. These include sugary foods and drinks, saturated fats and alcohol. Controlling your portion size is also important, especially so when eating foods that are higher in energy.
Basing meals around foods that have a low energy density will help to reduce your total energy intake.(11) A food’s energy density is the number of calories that it provides relative to its weight.(12) Fruits and vegetables have a low energy density. Foods that are higher in fibre will also make you feel fuller, helping you to eat less.
If you need to gain weight
There are a number of factors which may make it difficult to gain weight. Sometimes weight loss can be due to depression, or stress. In order to gain weight, the individual will have to create a calorie excess, aiming over a period of time to regularly consume more calories than their body burns.
This should be done while following general advice for healthy eating. This can be found in our booklet, Plant Based Nutrition. You can consume more calories by increasing your intake of calorie dense nutritious foods, such as houmous, nuts, tahini, avocado and dried fruits. You can also increase the total amount of food that you consume. Make sure you eat at least three meals every day. Eating snacks or additional mini-meals will also help to increase your total calorie consumption. Always have food available and make time for food shopping and preparation as well setting aside enough time for mealtimes.
As already noted, exercise brings a number of health benefits. You should not avoid exercise because you want to gain weight. Instead, if you are not already physically active, you will find that increasing your activity levels can improve your mood.(13)
Books on vegan nutrition with sections relating to weight
Becoming Vegan by Belinda Davis and Vesanto Melina
Plant Based Nutrition and Health by Stephen Walsh
(1) Flegal K. M. Troiano R. P. Ballard-Barbush R. Aim for a Healthy Weight: What is the Target? The Journal of Nutrition 2001; 131, 440-450
(2) World Health Organization (WHO) Obesity and Overweight. WH0; 2003
(3) Wellens R. I. Roche A. F. et al. Relationships between the Body Mass Index and body composition. Obesity Research 1996; 4(1), 33-44
(4) Michels K. Greenland S. Rosner B. A. Does Body Mass Index adequately capture the relation of body composition and body size to health outcomes? American Journal of Epidemiology 1998; 147, 167-172
(5) Frankenfield D. C. Rowe W. A. et al. Limits of Body Mass Index to detect obesity and predict body composition. Nutrition 2001; 17(1), 26-30
(6) Yusuf S. Hawken S. et al. Obesity and the risk of myocardial infraction in 27 000 participants from 52 countries: a case-control study. The Lancet 2005; 366: 1640-49.
(7) http://www.nhs.uk/Livewell/loseweight/Pages/Appleorpear.aspx (accessed November 2010)
(8) Filozol C. Gonzalez C.Predictors of Weight Gain. Obesity Reviews 2000;1(1), 21-26
(9) Ravussin E. Obesity in Britain: rising trend may be due to “pathoenvironment”. British Medical Journal 1995; 311 (7019), 1569
(10) Fogelholm M. Kukkonen-Harjula K. Does physical activity prevent weight gain-a systemic review. Obesity Reviews 2000; 1(2), 95-111
(11) Prentice A. M. Jebb S. A. Fast foods, energy density and obesity: a possible mechanistic link. Obesity Reviews 2003; 4(4), 187-194
(12) Prentice A. M. Jebb S. A. Fast foods, energy density and obesity: a possible mechanistic link. Obesity Reviews 2003; 4(4), 187-194
(13) Hansen C. J. Stevens L. C. Coast J. R. Exercise Duration and Mood State. Health Psychology 2001; 20 (4), 267-275