Are Calorie Equations Accurate In Obesity?

Some people who are working on losing weight like the approach of a calorie prescription, which is the daily amount of calories in food/drink that they should not exceed in order to lose weight.

This calorie prescription starts with an estimation of Resting Energy Expenditure (REE), which equals the number of calories we burn at rest over 24 hours, and can be estimated by any of a number of equations that have been developed for this purpose.  These equations incorporate various factors that influence REE, including age, gender, height, and weight.  From there, we typically multiply the REE by an activity factor to calculate the number of calories a person needs in a day, and then usually subtract 500 calories per day in order to achieve an initial rate of weight loss of around 1lb (0.5kg) per week.  

Most of these equations were generated using normal weight individuals, including very few people who carry excess weight.  But are these equations accurate in people with obesity?

A study, published in the International Journal of Obesity, evaluated a number of these formulae in 1,851 people with obesity, comparing the calculations to actual measures of Resting Energy Expenditure (using a technique called indirect calorimetry). 

They found that the accuracy of the equations to predict Resting Energy Expenditure was very low in people with obesity, and were even less accurate in people with a higher degree of obesity (BMI >40), especially females.   Even the Mifflin St-Jeor equation, commonly cited as the most accurate equation, performed poorly. These equations generally underestimated the calorie needs of participants by several hundred calories, with the degree of underestimation increasing with increasing BMI.

As these equations come in low, the calorie prescription ends up being too low.  This could mean that a person with obesity leaves their health care provider’s office with a calorie prescription that is too restricted – for example, that patient may be told that she should take in 1500 kcal per day in order to lose 1 lb per week, when actually her prescription should be 1900 kcal per day to lose 1lb per week.  For her, sticking to 1500 kcal per day would be very difficult – it may cause more rapid weight loss at the beginning but would be very tough to stick with.  

So why would these equations be less accurate in people with obesity? Fat tissue is less metabolically active than lean tissue (eg muscle), so having a higher proportion of fat can reduce accuracy of estimation using equations that were developed in a lean population.  It is also not clear which weight to use in these equations – actual weight, ideal weight, or adjusted weight.

Indirect calorimetry is a much better way to estimate calorie needs than equations, but has a price tag and limited availability. 

Clearly, we are in need of equations that are validated in people with obesity to estimate resting energy needs. 

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Does Intermittent Fasting Work?

One of the diet approaches that has really taken off in popularity is Intermittent Fasting.  Essentially, this means that certain days/times you restrict eating (or don’t eat at all) and other days/times, you feast.  This can take the form of Alternate Day Fasting (fast one day and feast the next), restricting on some days (eg weekdays) and feasting on others (eg weekends), or restricting eating to only a few hours each day.

Most studies showing benefit of intermittent fasting have been of very short duration (less than 12 weeks) – and let’s face it, just about anything can work over this very short term.  Now, a one year randomized controlled clinical trial has investigated whether intermittent fasting works.

The study, published in JAMA Internal Medicine, is quite a beautifully conducted trial (in my opinion), randomizing 100 people with obesity to one of three groups:

• Alternate day fasting: 25% of energy needs on fasting days, and 125% of energy needs on non fasting days
• Daily calorie restriction: 75% of energy needs on all days
• Control group: no intervention (they received 3 months of free weight loss counselling and a 1 year free gym membership at the end of the study)

Participants followed the above for the first 6 months of the study, which was the weight loss phase. 

For the second 6 months, the focus was on weight maintenance. Calorie needs were reevaluated (because we need less calories to maintain weight following weight loss), and the groups proceeded as follows:

• Alternate day fasting: 50% of energy needs on fasting days, and 150% of energy needs on non fasting days
• Daily calorie restriction: 100% of energy needs on all days
• Control group: no intervention

For the scientists in the audience: Total daily calorie needs were assessed using doubly labeled water, assessed at baseline and again at the start of the weight maintenance phase (t=6 months).  Analysis was by intention to treat.

At 12 months, the rate of dropout from the study was highest in the alternate day fasters at 38%, compared to 29% in the daily calorie restriction and 26% in the control group.

They found that the weight loss between the alternate day fasting and daily caloric restriction were no different at 6 months or 12 months.  Weight loss was 6.0% greater than the control group at one year in the intermittent fasting group, vs 5.3% greater than the control group in those on daily calorie restriction.   Other than a slightly higher bad cholesterol (LDL) in the intermittent fasters, there were no differences in any metabolic parameter.

While the study is small, it is the longest and largest clinical trial of alternate day fasting to date. 

BOTTOM LINE: The results of this study suggest that alternate day fasting is no better than daily calorie restriction for weight loss, and that the likelihood of sticking to the diet is lower with alternate day fasting.

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Let's Take ACTION - Barriers To Effective Obesity Management In Canada

Obesity is a chronic medical condition that affects 25% of Canadian adults. As we know from the recently released Canadian Report Card On Access to Obesity Treatment, we are doing very poorly in terms of providing publicly funded access to treatment for obesity.

So what are the barriers that are preventing people with obesity from getting access to obesity care?  In addition to collecting important statistics in the Canadian Report Card, we also need to understand barriers from the perspectives of people living with obesity as well as their health care providers.

The ACTION study is the first nationwide study in Canada to investigate barriers to effective obesity management from the perspective of people with obesity, healthcare providers, and employers who provide health programs or health insurance coverage.  This study aims to generate insights to guide collaborative action to improve care, education, and support for people with obesity, and to provide evidence upon which to change how patients, health care providers, and employers treat obesity.

The ACTION study steering committee (of which I am a member) has been working to construct questionnaires that will be deployed to patients, health care providers, and employers across the country, to gather information on these important topics.

By understanding these perspectives, we hope to improve communication, education, and break down barriers to allow better access and provision of care for people with obesity.

Stay tuned for the results of this study early next year!


Disclaimer: The ACTION study is funded by Novo Nordisk, the maker of anti obesity medication Saxenda (liraglutide 3.0mg). 

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Do GMO Foods Cause Obesity?

Genetically modified organisms (GMO) refers to any living thing that has had its DNA modified by genetic engineering techniques.  GMO foods have been developed to be resistant to pests and herbicides, and/or for better nutritional content.   With the introduction of GMO foods, we have seen a parallel rise in obesity rates.  Could GMO foods have a role in this?

There is very little data on this issue. One study looking at American food trends and obesity found that consumption of corn products correlates with the rise in obesity.  Most American corn that is grown is genetically modified - so is it an increased calorie intake from corn products, or that it is genetically modified, that may be responsible correlation?  Or is the correlation purely coincidental? More research needs to be done.

A comprehensive review of dietary and policy priorities for cardiovascular disease, diabetes, and obesity published in the journal Circulation in 2016 found that existing evidence does not support that GMO food causes harm, but that the data are limited.   They point out that any potential effect of a GMO food on human health (positive or negative) would relate to specific compositional changes in the food, not to the GMO method itself.

As these authors state:

Based on current evidence, whether a food is organic or genetically modified appears to be of relatively small health relevance in comparison with the overall types of foods and diet patterns actually consumed. 

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Breaking News - Canada's Report Card On Access To Obesity Treatment

Obesity is a treatable chronic medical condition that affects over 25% of Canadian adults.  But how well are we doing at treating obesity in Canada?

Today, the Canadian Obesity Network has released the Report Card On Access To Obesity Treatment For Adults In Canada. This is the first rigorous assessment of the degree to which Canadians with obesity can access publicly funded treatments such as dieticians, psychological counselling/support,  medically supervised weight management programs, medications for obesity, and bariatric surgery.

The Report, not unexpectedly, showed that access to care for obesity in Canada is extremely limited.

• There is very little publicly funded access to dietary counselling, mental health support, cognitive behavioural therapy, or exercise professionals. 
• There is no public coverage for anti-obesity medication, and only about 20% of private medical plans offer coverage. 
• Bariatric surgery is available to only 1 out of every 183 adult Canadians per year who may be eligible for it (this varies widely by province, with the best availability of 1/90 in Ontario, and the lowest availability of 1/1,312 in Nova Scotia).  

So why is access to obesity care in Canada so poor?

1.  Despite the Canadian Medical Association declaring that obesity is a chronic medical condition (and not a lifestyle issue) in 2015, neither Health Canada, nor the federal government, nor any provincial governments have followed suit. This results in a lack of policies that support obesity care.

2.  Medical schools have little to no formal obesity training, and very few Canadian doctors pursue additional obesity training of their own accord.   Only 40 out of 80,544 doctors in Canada have completed certification through the American Board of Obesity Medicine. (there is no formal obesity training equivalent in Canada)

3.  There remains a powerful and pervasive obesity stigma in Canada, which has been shown to be even worse in the medical community than in the general population.  Person-first language is often not used in government resources nor in medical literature - meaning that obesity is used as a description of a person rather than as a diagnosis. (The correct terminology is a 'person with obesity', not an 'obese person'.)

4.  Government programs tend to focus on health promotion and obesity prevention, which is important, yes, but with a lack of attention to helping people who have obesity and need treatment for it.


So, where does this leave us?  The Report recommends:

• Government, employers and the insurance industry need to adopt the position that obesity is a chronic medical condition and orient their approach and resources accordingly;
• Government needs to recognize and help break down weight bias and stigma;
• Obesity training for health care professionals needs to increase;
• Governments need to increase funding and access to interdisciplinary care, weight management programs, anti-obesity medications, and bariatric surgery; 
• The Canadian Clinical Practice Guidelines, last published in 2007, need to be updated (and we are starting work on this!)

It seems we have a lot of work to do. 

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Could Yo-Yo-Ing Weight Increase Risk Of Heart Attack?

In the effort to manage excess body weight, many people have experienced the 'yo-yo' effect: start a diet, weight goes down... end the diet, weight goes back up (and then some, in many cases).  We already know that this fluctuation in weight is damaging to metabolism, in that our bodies essentially remember the highest weight we have ever had, making powerful hormonal and metabolic changes to drive us back up to our highest weight.  Now, a study in the New England Journal of Medicine demonstrates that fluctuation in body weight is associated with a higher rate of heart attack and death in people who have coronary artery disease.

The study evaluated fluctuations in body weight amongst 9,509 people with heart disease, who were enrolled in the TnT trial of cholesterol medication atorvastatin, taking the opportunity to evaluate whether fluctuations in weight made a difference in terms of risk of having a cardiovascular event.  In a post hoc analysis, they found that the greater the weight fluctuation, the higher the risk.  Specifically, for every 1 Standard Deviation (SD) in weight, there was a 4% increase in risk for any cardiovascular event, and a 9% increase in risk of death, independent of other cardiovascular risk factors.  Among patients in the top 20% for fluctuations in body weight, there was an 85% higher risk of a cardiovascular event and over a double increased risk of death, compared to those in the lowest 20% for fluctuations in body weight.  The risk associated with weight fluctuation was higher in those with obesity or overweight, compared to those of normal body weight. Also, a greater body weight fluctuation was also associated with a higher risk of developing type 2 diabetes.

One wonders whether these findings could simply reflect that people who had wide fluctuations in weight were sicker in general (eg big weight loss with illness), though this clinical trial did exclude people with a poor prognosis. The study also did not assess whether the weight fluctuations were intentional (eg dieting) vs unintentional (eg illness).

We cannot infer causality from this study - in other words, we can't be sure that the weight fluctuations were the cause of the increased cardiovascular events - but the association between weight fluctuation and cardiovascular events was nevertheless strong.  Given these findings, it seems more important than ever to avoid yo-yo weight changes by making permanent lifestyle changes rather than engaging in temporary solutions/programs to optimally manage weight.

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After Bariatric Surgery - Patients' Perspectives

There is no doubt that bariatric surgery is a hot topic of research these days.  Most of this research focuses on the medical benefits that can be enjoyed after bariatric surgery, such as improvements in diabetes control, high blood pressure, sleep apnea, and so forth.  Much less qualitative research has been done - the kind of research that looks at things that are hard to measure with numbers, such as psychological effects and changes in quality of life. Most of the qualitative information that has been published is on small groups of individuals, and it is challenging for patients or clinicians to synthesize this smattering of data as a whole.

Coulman and colleagues recently collected information on this topic in the first systematic review of qualitative research in the bariatric surgery field.  Published in Obesity Reviews (and free to download!), they included 33 studies reporting on the patient perspective on living with the outcomes of bariatric surgery.

Three themes were identified:

1.  Control.  Patients reported making the decision to undergo bariatric surgery to gain control over eating, weight, and health.  In general, a feeling of improved control was experienced in the first year after surgery, but after a year, there was less of a sense of physical control (described as 'stomach control'), and it became more about relying on their own 'head control' to manage food intake.

2. Normality.  A sense of 'normality' was something that many patients were striving for after bariatric surgery - lives less burdened by physical and psychological ill health, ability to participate in normal everyday activities, and what patients described as a more 'socially acceptable' appearance.  While many people felt more 'normal' after surgery, there were also several issues identified that challenged patients' desire to feel 'normal'.  This included a change in their own or others' perceptions of their bodies, unpleasant gastrointestinal side effects (eg vomiting or diarrhoea), not being able to eat like others, and loose hanging skin.

3.  Ambivalence. Patients reported that while some things changed for the better, other changes were difficult to cope with or adapt to. This included physical pros (improvement in metabolic health) and cons (gastrointestinal and nutritional side effects of surgery).  This also included psychological pros (improvement in depression, self esteem, control) and cons (eg continued depression and self esteem issues with a realization by some that bariatric surgery was not going to fix these issues; challenges of finding ways other than food to cope with emotions; feeling a loss of protection from the outside world and a feeling of vulnerability with weight loss).

This review is a treasure trove of information, including quotes from patients, and is a great read in its entirety.   These findings highlight that while bariatric surgery is an excellent treatment strategy for some people, for others it may not be the best choice.  These findings certainly speak to the need for long term follow up for patients who have had bariatric surgery, including long term psychological and nutritional support.

As the authors write: Surgery was not the end of their journey with obesity, but rather the beginning of a new and sometimes challenging path.

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