Slimming and Weight Reduction

 
Introduction
It is now considered that 43% of British men and 33% of women are overweight or obese (British Heart Foundation). Worryingly, the problem is likely to become more prevalent over the coming years.  
 
The repercussions of being overweight or obese are increased risk of many chronic diseases such as diabetes type 2, cardiovascular disease, and arthritis.
Similarly, there are often associated increases in levels of depression and reduction in overall quality of life.
 
On top of this many people who are overweight, wish to reduce weight for reasons of image and self esteem as much as for improvement in general health.
 
Most scientific and clinical authorities now agree that the only way to lose weight and maintain that weight reduction is to expend more energy than is consumed. This means:
 
     Reduction in calorific intake
                and/or
     increase in activity levels.
 
 
As a result of the population wide increase in weight, the pressure very often for individuals to reduce weight is strong and as such a large industry has grown up around the provision of products to assist in this weight reduction.  
 
Within the realm of dietary supplements there are a number of product and nutrient types which are promoted to assist in a weight reduction programme. There is now accumulating evidence that some nutrients may have specific benefits in helping to reduce weight and the supplementation of these nutrients as an adjunct to a calorie controlled diet is an option worthy of consideration. 
 
However, some product types have very little basis for effect and are therefore unlikely to deliver the expected weight loss benefits.
 
A brief review of the nutrients which have purported weight loss benefits are outlined below. They have been divided into those where there is substantial evidence of benefit and those where benefits have less proof. 
 
Nutrients with substantial evidence of benefit:
  • High protein, low calorie meal replacements
  • Palm and oat oil extracts ( Fabuless)
 
Nutrients with some evidence of benefit:
  • Conjugated linoleic acid (CLA)
  • Pine nut extract (Pinnothin)
  • Garcinia cambogia (hydroxycitric acid)
  • White kidney bean extract
 
Nutrients with little or no evidence of benefit
  • Guarana, Mate extracts (caffeine)
  • Herbal mixtures containing: Boldo, Dandelion and Fucus (seaweed extract)
  • Chromium
  • Apple Cider Vinegar

Nutrients with substantial evidence of benefit:

 

HIGH PROTEIN, LOW CALORIE MEAL REPLACEMENTS 

These products typified by the Slim-Fast brand, and similar products do not strictly come under the dietary supplement banner, but are often grouped in the same shelving in many supermarkets and pharmacy chains. In addition, these products often contain significant levels of added vitamins and minerals and more recently other nutrients which may have additional weight reduction benefits.  

Typically these products are powders which are made up with water or skim milk into flavoured milk shake type drinks. They normally provide between 200-250 calories per meal. As such the substitution of one of these drinks in place of an average meal containing between 500 and 900 calories would be a very effective component of a calorie controlled diet, indeed may by itself be sufficient dietary modification to produce weight loss over a period of time.     
 
Many well conducted scientific trials in overweight and obese adults have demonstrated effectiveness of these types of product, and also that the mechanism of using a meal replacement is more effective than simply reducing calorific intake to the same level but over the whole three meals. Thus in an analysis of several trials over a period of three months nearly six extra pounds of weight was lost in people who used meal liquid replacements as part of their calorie restricted diet compared to those who had  the same intake of calories spread over three conventional meals. (Data from Heymsfield et al 2003)
 
Furthermore many of these products supply a significant contribution to the benchmark recommendation of 100% RDA intake of vitamins. Indeed some provide the entire level and therefore offer the opportunity of saving on a separate multivitamin and mineral supplement.
 
To be effective, at least one but more often two normal meal needs to be replaced with the drink each day, and the calorie deficiency resulting is not replaced either by snacking or by additional calories consumed in the other one or two normal meals. If adhered to then weight reduction should be apparent within 1-2 weeks, but like with any diet should be maintained for with gradual and consistent weight loss over a minimum three month period.
 
PALM AND OAT OIL EXTRACT (FABULESSTM)
 
This product is an emulsified palm and oat oil mixture which is slow to digest, and as such reaches the last part of the small intestine still intact. The presence of the undigested fat this far down in the intestine sends signals to our appetite sensors to reduce the sensation of appetite for the following meal, where the idea is that less is then eaten.
 
This product has several well conducted trials which demonstrate this effect in reducing calorific intake by between 12.5 and 30% in meals following the consumption of the product. Some of these studies have then demonstrated that this effect either assists in weight loss or helps prevent weight gain following initial weight reduction. 
 
About 5g of the fat emulsion is required per day and as the appetite suppression effect appears to last for more than 8 hours then taking at breakfast or lunchtime is best.
 

Nutrients with some evidence of benefit:

 

CONJUGATED LINOLEIC ACID (CLA)

This is a type of fatty acid normally found in animal and dairy products but now produced from safflower oil. Several well conducted studies have shown that CLA is effective in helping either reduce weight or redistribute the fat/lean ratio in adults when part of a calorie controlled diet particularly if there is also an elevation of exercise level. 

Interestingly, the most evidence for CLA lies in it resulting in a shift in the ratio of the weight to more muscle and less fat, even if the overall reduction of weight is only moderate. 

The dose required to deliver the effects shown by CLA are between 1.7 and 3.6g per day with faster more consistent benefits coming from the higher dosage forms.

Supplementation with CLA is only likely to deliver these benefits if part of a calorie controlled diet and also if exercise levels are increased. The period of supplementation necessary in order to observe noticeable benefits is between 6 and 12 weeks.

WHITE KIDNEY BEAN EXTRACT

The extract of this type of bean contains ingredients which block the breakdown of starch in the intestine, by inhibiting the digestive enzymes which perform this task. In meals which contain a high level of readily broken down starch e.g bread, pasta, potatoes etc. this characteristic could be useful, and theoretically would mean that a significant amount of starch in the meal would not be absorbed and would be eliminated with bowel movement.  There does appear to be however, the same level of appetite satisfaction compared to that found if the starch was fully digested.  

There is one well conducted trial demonstrating the effects of white kidney bean extract and several a limited amount of others which indicate an effect. The amount of kidney bean extract required to deliver the effect is a minimum of 450mg and this needs to be taken just prior to a meal or meals rich in starch.

Again this product would be more likely to deliver the intended benefits as part of a calorie controlled diet

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PINE NUT EXTRACT (PINNOTHIN)

This is a relatively new addition to the nutrients available to assist in weight reduction. Like the palm and oat extract product, this is an extract of pine nut and again is works by blunting the sensation of appetite with the effect of depressing calorific intake in subsequent meals. Again there is some good accumulating evidence in huan weight loss trials which demonstrate positive effects with this product.

Between 2-4g of this product is necessary to deliver the intended benefit. The product is in various forms and can be taken 2-3 hours before a meal to suppress appetite for that meal. Alternatively, when taken with food, it will suppress appetite for that meal and also the subsequent meal several hours later.

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GARCINIA CAMBOGIA (HYDROXYCITRIC ACID)

This is an extract from the Malabar tamarind tropical fruit, and is native to India. Initial trials on this product showed some positive effects in weight reduction, due to the product purportedly having the ability to accelerated fat burning, and reduce fat storage.

Subsequent trials have not supported this initial work, so the advice would be to not consider this product reliable in delivering weight loss results.

Approximately 750mg of hydroxycitric acid per day is necessary to deliver any intended benefit.

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Nutrients with little or no evidence of benefit:

   

HERBAL MIXTURES CONTAINING: BOLDO, DANDELION AND FUCUS (SEAWEED EXTRACT)

Many slimming supplements which are on the market are classed as traditional herbal remedies which have been allowed to claim a benefit in weight reduction due to historical useage which may go back several decades or longer.

However, the use of these traditional herbal remedies to assist in weight reduction appears to have little or no supporting credible scientific evidence at all. Many contain dandelion which has mild diuretic properties and hence may stimulate some temporary fluid loss.

Boldo is traditionally used as a detoxifying herb again with little supporting evidence. Fucus or seaweed contains iodine and so may have mild thyroid stimulating effects, but probably no more than would be the case than if a multivitamin containing iodine at 100% of the RDA was supplemented.

Overall, the SC panel see little or no merit in these products.

GUARANA, MATE AND OTHER CAFFEINE BASED SUPPLEMENTS

Guarana, and mate tea are South and Central American plants which have a caffeine content similar to coffee beans and as such produce the same physiological effects as caffeine.

Caffeine is a metabolic stimulant and studies have conclusively demonstrated that it can increase metabolic rate for up to 24 hours and also that it potentially stimulates an increased rate of fat ‘burning’  

As such there is a theoretical basis to the use of caffeine in support of a weight loss programme. However, the evidence from human trials of actual weight loss effects is thin with only one small trial showing benefits and very little evidence of that trial being repeated.

Many of the weight reduction trial using caffeine also provided ephedrine containing herbs. These products did show weight reduction benefits, but the stimulant ephedra is associated with significant adverse side effects and as such these products are banned in the UK.   

The level of caffeine necessary for any likely effects to be shown is a minimum of 200mg per day which is the same as two cups of coffee.

Overall the view of the SC expert panel is that products with these ingredients are unlikely to provide additional benefits to a weight loss programme.

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CHROMIUM

Chromium deficiency is associated with hyperglycemia, (elevated blood sugar level) and also elevated insulin and blood fat levels. As such, chromium is thought to play a role in carbohydrate and fat metabolism, and as such is included in many weight loss products. However, there are no known human trials where chromium has been found to be beneficial in a weight reduction programme for either diabetic or non-diabetic individuals.

As such products containing chromium should be viewed as offering benefit in increasing chromium intake, but that there is probably little or no benefit in weight loss.

FIBRE AND GUM COMPLEXES (DESCRIBED AS FAT BINDERS, FAT BLOCKERS ETC)  

There is good evidence that significant increases in the fibre content of the diet by way of consumption of less energy dense high fibre foods such as fruit and vegetables can assist in a weight reduction programme. However this is a complex effect involving lower calorific intake combined with greater feeling of fullness produced from these types of foods. A part of this effect is the characterisic of some types of viscous soluble fibre to form become gum like when ingested.

As such some products now incorporate these gummy materials derived from either plant fibre or gum complexes, or chitosan derived from crustacean shells into capsules and tablets as slimming aids. These products are purported to work either by absorbing water in the stomach (the gum based products) and so promoting a feeling of fullness and hence lowered calorific intake which is reasonable or by binding to fat in the stomach resulting in it not being absorbed and passed out with the faeces which is a much more dubious mechanism.  

One of these types of gum, guar gum has been extensively tested in weight loss trials, but in an averaged analysis of 11 trials no benefit in weight loss was found.

Psyllium fibre has also shown no benefit in weight loss trials. 

Glucomannan, in dosages of 3-4g per day has been shown in trials to produce a modest weight loss, and so may be worth considering.

Chitosan, was shown by one group to be effective in weight loss trials, but other research groups have failed to replicate these effects.

Other fibre containing products have some very small studies not subject to peer review which show some evidence of greater levels of excreted fat in subjects taking the supplement, but until these studies are confirmed by more rigourous trials, the reliability of this evidence is dubious.    

Overall, the SC expert panel believes these types of products have little credible supporting evidence and so cannot be routinely recommended as part of a weight reduction programme. Also, in many products the level of  these ingredients are often too low to deliver the intended effect and tend to be very expensive for what they do contain.

APPLE CIDER VINEGAR

Apple cider vinegar is simply vinegar made from apple cider. It will be acidic and may have an effect in having a modest acidifying effect in the stomach. Despite being promoted as a supplement to promote or assist in weight loss, there is no known scientific evidence to support such claims, and no real mechanism which is credible which may explain any weight loss effect.

As such, the SC expert panel opinion is that apple cider vinegar is very unlikely to deliver any benefit in any weight reduction programme.

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