In a previous blog (1) I was highly critical of the article on obesity which was written by The Guardian health editor, Sarah Boseley (2). It now emerges that the article was based on a book by Boseley which has just been published (3). Furthermore the launch of the book has been supported by an interview with the government’s chief adviser on obesity, Susan Jebb, who is professor of diet and population health at Oxford University (4). In this she is quoted as saying that people who are overweight may have to resign themselves to a lifetime of strategic dieting. The object should be to lose at least 5% of body weight at least every 5 years.
Jebb’s position is based on a number of assumptions all of which are extremely dubious. These are;
- That being overweight or obese is damaging to health
- That weight can be lost by reducing calorie intake
- Weight loss will be beneficial to health.
I will consider each of these in detail.
Body Mass Index (BMI) which is calculated using information on height and weight is used to determine the different categories of overweight/obesity. Hence we have:
- BMI 20-25 Normal
- BMI 25-30 Overweight
- BMI 30-35 Mildly obese
- BMI >35 Seriously obese
There is now extensive and convincing evidence that the greatest life expectancy is experienced by those who are classified as “Overweight”. In addition, there is no reliable evidence that there is any reduced expectancy even in those who are mildly obese (5). It is true that those who are seriously obese do have an increased mortality but the picture changes when the effect of physical fitness is incorporated.
The information in Table 1 shows that for those who are physically fit the death rates are pretty much the same irrespective of BMI. However for those who are not physically fit, the picture is totally different. For all categories the death rates are very much greater when compared with those who are fit but the greatest differences are shown for those with a BMI >35, which is not surprising. But what is especially interesting is huge difference in those with the normal BMI <25. This is highly significant is that those who on the basis of BMI alone would be regarded as healthy actually includes the unfit with a relatively high death rate.
This information demonstrates that if the government genuinely wishes to improve public health then it should forget about advising people generally to lose weight but place much greater emphasis on achieving a reasonable degree of physical fitness. Encouraging people to walk about one mile a day or take up activities such as dancing or gardening are likely to have enormous benefits even if body weight does not alter.
EFFECT OF PHYSICAL FITNESS ON DEATH RATES (PER/1000 PERSON-YEARS) FOR DIFFERENT BMI CATEGORIES
Nevertheless it is true that there are some people who are extremely overweight with BMIs which are >35 that are also inactive. Part of their problem may well be that they are so heavy that even a reasonable degree of activity is not feasible. There can be little doubt that some loss of weight would be beneficial and perhaps enable them to take to take some exercise. However the conventional approach which focuses on calorie reduction just does not work! This has been established by numerous studies (5).
In the 1990s an NIH Technology Assessment Conference Panel in the USA concluded that as many as 40% of women and 24% of men were trying to lose weight at any given time (6). Many have tried a variety of methods, such as diets, exercise, behaviour modification, and drugs. In controlled settings, participants who remain in weight loss programs usually lose approximately 10% of their weight. However, one third to two thirds of the weight is regained within 1 year, and almost all is regained within 5 years. For many overweight persons, achieving and maintaining a healthy weight is a lifelong challenge.
Despite persistent failure, the official advice in many countries continues to focus on calorie reduction. Invariably this is achieved by reducing the intake of fat on the grounds that fat is a concentrated source of calories. The inevitable result is an increase the proportion of carbohydrate-containing food and very often an increase in the absolute amounts. There is no question that a diet which is high in sugars and refined carbohydrates results in a rapid release of glucose, which is soon reflected in a raised glucose level in the blood. There is now convincing evidence that a diet of this type leads to the deposition of body fat and if it is maintained over a long period, it is virtually certain that the person will become obese. This explains why it is almost impossible to lose weight using a diet which is high in carbohydrates and low in fat. The reality is the only people who succeed in the short term are those who effectively starve themselves. Therefore it is not in the least surprising that invariably any weight lost is eventually re-gained.
What is even worse is that those few who succeed in losing weight by this approach are probably damaging their health (7). For example, a study conducted in Southern California monitored 140 men and 90 women with and without diabetes aged between 40 and 79 when the work commenced in 1972-1974. The follow-up was done after 12 years. It was found that those who lost 4kg or more had an increased death rate compared those who did not lose weight (Table 2). Similar results were obtained after excluding cigarette smokers, those who were depressed, had a low BMI and those who died within 5 years of losing weight(8).
TABLE 2 CHANGE IN DEATH RATE AS A RESULT OF LOSING WEIGHT
Those who adopt the calorie reduction approach very often end up “weight cycling” with repeated weight loss followed by re-gain. It has been established that these people have a very much higher death rate than those who steadily gain weight throughout life (9).
On the other hand, diets which are low in carbohydrates and high in fat are extremely successful in achieving weight loss. What is even more significant is that these diets are also very effective in reducing risk factors for heart disease and various cancers. For anyone who would like further information these books will be most illuminating (10,11,12).
Although the authorities have been very resistant to changing the official advice, there has been a significant breakthrough in Sweden where a report from the Swedish Council on Health Technology Assessment which concluded that a low-carbohydrate diet is clearly more effective than today’s conventional advice (13).
As long ago as the 1860s, William Banting, a London undertaker, after trying all sorts of remedies eventually found that a diet low in carbohydrates and high in fat enabled him to overcome his “corpulence”. Prior to this he could not even bend down to tie his shoe laces (14). He published a pamphlet, which proved to be very popular because people recognized how successful his approach was. One hundred and fifty years later we still have not learned the lessons!
- Sarah Boseley (2014) “The Shape we’re in: How Junk Foods and Diets are Shortening Our Lives” Faber &Faber
- Ann Intern Med. (1992)116(11) pp 942-949. doi:10.7326/0003-4819-116-11-942
- N M Wedick (2002) Journal of the American Geriatric Society 50 (11) pp 1810-1815
- Vanessa A Diaz (2005) Journal of Community Health 30 (3) pp 153-165
- Gary Taubes (2007) “The Diet Delusion” Vermillion: London
- Zoe Harcombe (2010) “The Obesity Epidemic” Columbus
- Nina Teicholz. (2014)“The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet” Simon & Shuster: New York