One of the greatest barriers to weight loss is conventional dietary advice to eat more to lose weight. This was covered in a previous post “Time Dependence”. This advice sounds completely contradictory because it is. Nevertheless, the media is full of unhelpful advice to eat more to lose weight. The reason, I believe, is that nobody makes any money when you eat less.
One of the most pervasive pieces of advice out there is to eat more fruits and vegetables (F/V) in order to lose weight. There is no denying that F/V are healthy foods. However, if our goal is to lose weight, then it logically follows that deliberately eating more of something is not beneficial unless it replaces something else less healthy.
However, that is not what nutritional guidelines recommend. For example, in the World Health Organization Report “Diet, nutrition and the prevention of chronic diseases:report of a Joint WHO/FAO Expert Consultation” on page 68 it writes:
For children and adolescents, prevention of obesity implies the need to:
- Promote the intake of fruits and vegetables
The 2010 Dietary Guidelines for Americans also stresses the importance of increasing intake of F/V. In fact, this recommendation has been part of the Dietary Guidelines since its very inception. The health benefits of F/V stem from what they add and what they subtract from our diets. F/V are high in micronutrients, vitamins, water and fibre. They may also contain anti-oxidents and other healthful phyto-chemicals. This is likely the reason why we are reminded to eat more F/V.
What is not explicit is the fact the increased intake of F/V is expected to displace higher energy, less healthy foods from our diet. Because most F/V have a low energy density (low calories in a given volume), and have high fibre, it is assumed that satiety will increase and therefore we will eat less other foods that are more energy dense.
If this is the main mechanism of weight loss, then our advice should be to “replace bread with vegetables” for instance. But it is not. Our advice is simply to increase F/V intake. Is this really true? Can we really eat more to lose weight?
A recent paper shed some light on this issue. Entitiled “Increased fruit and vegetable intake has no discernible effect on weight loss: a systematic review and meta-analysis“, it was published in Aug 2014 AJCN. In this paper, researcher gathered all available studies on the intake of F/V intake and weight gain.
What they found should not be a major surprise. The zero line on the graph indicates no net benefit or harm from increased F/V. No individual study was able to show that there was any significant benefit, and the sum total of all the studies also showed no benefit. Taken all together, this is very strong evidence that the advice to eat more to weigh less is simply not sound. To put it simply, eating more F/V does not make you lose weight. You cannot eat more to weigh less.
Why do we give such obviously-wrong advice? Starts with an M and rhymes with honey. Because nobody makes any money when you eat less and therefore buy less F/V. Companies want to sell you fruit/ vegetables/ supplements/ calcium/ omega 3/ vitamin D/ snacks/ meal replacements. That is how they make money. Nobody sells any books telling you to eat less. We don’t want to hear what we already know.
So, should we eat more fruits and vegetables? Yes, definitely. But only if they are replacing other unhealthier foods in your diet. Replace. Not add. Losing weight boils down to reducing insulin levels. Eating more of something, even as healthy as fruits and vegetables simply does not achieve that goal.
This is also reinforced by the recent study “Fruit consumption and the risk of type 2 Diabetes” published in the British Medical Journal 29Aug 2013. Looking at 3 large prospective cohorts (Nurses Health Study 1 and 2, and the Health Professional Follow Up), the researchers from Harvard looked at the risk of type 2 diabetes with the consumption of whole fruits and fruit juice.
With close to 190,000 subjects over 2 decades of follow up, this was a huge study. After adjustment, the pooled hazard ratio for every 3 servings/week of fruits was 0.98. In English, this means that over 12 years or so of follow up, eating an extra 3 servings of fruit per week reduced your risk of type 2 diabetes by 2%. The risk for fruit juice was 1.08 meaning an extra 8% risk with 3 servings of fruit juice.
Clearly, adding fruits to the diet is not an extremely beneficial dietary strategy. But not all fruits are the same. The glycemic index, as well as the amounts of fibre, vitamins and antioxidants all differ. This was a large enough study to allow individual fruits to be examined. One thought is that fruits with high glycemic index may not be as beneficial. This has often led to advice such as eat fruits except for bananas and grapes. In a stunning rebuke to the utility of the glycemic index, this study showed that grouping fruits by glycemic index was completely useless. Eating more high glycemic load (GL) foods lowered the risk of type 2 diabetes, whereas eating more moderate and low GL foods did not. This is completely contrary to what the glycemic index would predict.
What happens when you replace, not add? That is, if you were to replace 3 servings/week of fruit juice with whole fruit, would you see a benefit? Now you’re cooking with fire. Now you start to see a significant benefit for the prevention of type 2 Diabetes. But there is a wide range of effects depending upon the fruit in question.
Certain fruits such as blueberries are far more effective at preventing diabetes than others (cantaloupe and strawberries). Bananas and grapes, often avoided due to their high glycemic index, turn out to be fairly good in preventing diabetes. Replacing fruit juice with fruit resulted in the following reduction in risk of diabetes:
- Overall 7%
- Blueberries 33%
- Grape 19%
- Apples/ Pears 14%
- Bananas 13%
- Grapefruit 12%
The overall message is clear. Eating more to weigh less is a doomed strategy. You need to Replace, not Add.
Continue here to Hormonal Obesity XXII – The Incretin Effect
Start here with Calories Part I – How Do We Gain Weight?
See the lecture – The Aetiology of Obesity 3/6 – Trial by Diet
By The Fasting Method
For many health reasons, losing weight is important. It can improve your blood sugars, blood pressure and metabolic health, lowering your risk of heart disease, stroke and cancer. But it’s not easy. That’s where we can help.
By Jason Fung, MD
Jason Fung, M.D., is a Toronto-based nephrologist (kidney specialist) and a world leading expert in intermittent fasting and low-carb diets.