By Matt O'Neill, MSc(Nut&Diet), APD
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The scientific evidence on the benefits of dairy consumption on fat loss are stacking up, so if you're struggling with weight loss, it might be time to do a `dairy audit', to make sure you are getting enough dairy in your diet.
Dairy is a nutrient-rich food, well-renowned for its calcium content, which we all known is critically important for bone health. But as you'll read below, dairy products are shaping up to be equally important for fat loss, and weight maintenance.
Dairy products have many attributes which are well known to facilitate weight loss on a calorie-restricted diet, including:
• Low GI
• Good source of high quality protein
• Good source of dietary calcium
These qualities are well known to help weight loss on calorie-restricted diets, but there are many additional components in dairy products which actively facilitate fat loss.
The explanations below are a bit technical, but if you need convincing to include dairy in your MJ Plan - they are well worth the read.
Dairy products are high in protein - just 1 glass (250mL) of skim milk contains 9g of high quality protein. The unique balance of proteins in dairy products have been repeatedly shown to have beneficial effects on satiety and feelings of fullness after eating, which can reduce subsequent food intake at your next meal.
The protein fraction in cow's milk consists of whey and casein, two unique proteins which exert very different metabolic effects. Both proteins have been shown to suppress short-term food intake, which increases satiety . Whey protein is well-known to be beneficial for muscle building, especially after exercise, and has also been shown to result in the increased release of satiety factors such as cholecystokinin (CCK) and glucagon-like peptide (GLP-1) .
Whey protein contains a high percentage of Branched Chain Amino Acids, or BCAAs, which include leucine, isoleucine and valine. These are essential amino acids which regulate muscle synthesis, and promote a favourable body composition by building muscle and reducing body fat .
The search for `bioactive components' in dairy continues, as Researchers try to identify compounds in dairy which help explain the beneficial effects on fat loss.
One such example are bioactive peptides (small protein fragments) which exert ACE inhibitor activity, which have been isolated in the whey component of dairy . Their inhibitory effect acts to reduce blood pressure (in the same way ACE inhibitors are used as pharmaceutical drugs), but has also been shown to reduce overweight and obesity in both rat and human studies.
Genes and the environment
Coeliac disease shares certain predisposing genes with autoimmune diseases, such as type 1 diabetes. These genes control how the immune system `recognises' and responds to foreign proteins and are fundamental for the disease to develop.
Genes alone are not enough to cause coeliac disease and environmental factors are thought to play an important role in `triggering' disease in those with genetic susceptibility. Some factors appear to increase coeliac disease risk, such as rotavirus infection in infancy, while some may reduce the risk. Breastfeeding at the time gluten is introduced to an infant, for instance, may protect against developing the disease.
Dairy & fat loss
A comprehensive review  in 2009 summarised the findings on the role of calcium and/or dairy products on weight management, and found that the majority of studies showed a significant benefit with regard to weight loss and maintenance.
The evidence appears to be adding up:
• Population studies show that low calcium and/or dairy intake is associated with greater body fat as well as greater risk of weight gain over time .
• Dairy consumption has been shown to protect muscle mass on calorie-restricted diets .
• Preliminary studies show that maintenance diets that are high in dairy have been shown to minimise short-term regain of body weight following weight loss compared to a low dairy diet .
• Observational and population studies show an inverse association between dietary calcium and/or dairy intake and body weight in all life stages (children, adolescents, adults) .
• One study showed that when 3 groups of people were randomized to 3 different diets - low calcium, high calcium from supplements or high calcium from dairy - the greatest weight loss was seen in the high dairy group, despite the high calcium and high dairy groups having similar calcium intakes .
The strongest evidence for an association to date comes from the Women's Health Initiative Study  which was published in 2007. This randomized trial of over 36,000 postmenopausal women was designed to test the hypothesis that calcium and vitamin D are associated with less weight gain over time, and the results found that this hypothesis was strongly supported.
Many other studies show the benefit of the inclusion of dairy in the diet and fat loss. Of particular interest is a recent randomized controlled trial7 on obese people on energy-restricted diets which showed that the group allocated to a high dairy diet (3 serves of yoghurt per day, totaling 1,100mg calcium) had significantly greater decreases in not only total body fat, but visceral fat. This reduction in visceral fat led to greater reductions in waist circumference compared to the control group, who remained on a low calcium diet.
A study published in 2011 which looked dietary factors associated with 7-year weight change in over 120,000 Americans found that yoghurt consumption was strongly inversely associated with long-term weight gain (i.e. yoghurt-consumers had the lowest rates of weight gain in the study period) . Interestingly, of all the foods that were shown to have an inverse association with weight gain (including whole grains, vegetables, fruits and nuts), the association with yoghurt was the strongest.
Glucose tolerance and insulin sensitivity
Dairy has also been shown to improve glucose tolerance , which may be beneficial for people with impaired glucose tolerance, insulin resistance and type 2 diabetes.
One large observational study  in young adults showed that the 10 year incidence of the insulin resistance syndrome and type 2 diabetes in overweight subjects was inversely associated with dairy consumption, i.e. the overweight people who had high intakes of dairy had a lower risk of developing insulin resistance and type 2 diabetes 10 years into their adult life.
Reductions in circulating insulin have also been documented; however, these results may not be direct benefits of dairy, as weight loss is known to improve glucose tolerance and insulin levels.
Calcium & fat loss - the mechanism
Physiologically, low calcium diets are known to cause an increase in 2 hormones, known as Parathyroid hormone (PTH) and calcitriol, which is the active form of vitamin D. These two hormones act together to increase the amount of calcium in the blood, thus restoring calcium balance and minimising the breakdown of bone under low calcium conditions.
Experiments on both human and mouse fat cells have shown that these two hormones also act on the fat cell, causing an increase in calcium within the fat cell, which in turn stimulates fat storage by increasing the expression of genes involved in fat synthesis .
Conversely, high calcium levels in the blood cause a decrease in the amount of calcium within the fat cell, which promotes fat breakdown, inhibits fat storage and increases heat production . This pathway provides a direct explanation for the role of calcium in dairy products in the regulation of body fat stores.
Put simply, dietary calcium may helps fat cells burn off more fat.
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2. Pereira, M.A., Jacobs, D.R.Jr., Van Horn, L., Slattery, M.L., Kartashov, A.I. & Ludwig, D.S. Dairy consumption, obesity, and the insulin resistance syndrome in young adults: the CARDIA Study. Journal of the American Medical Association. 2002;287(16):2081-2089.
3. Zemel M.B. The role of dairy foods in weight management. J Am Coll Nutr. 2005;24(6 Suppl):537S-546S.
4. Heaney R.P., Rafferty K. Preponderance of the evidence: an example from the issue of calcium intake and body composition. Nutr Rev 2009;67(1):32-39.
5. Zemel M. Dietary calcium and dairy products accelerate weight and fat loss during energy restriction in obese adults. Am J Clin Nutr 2002; 75(suppl):342S-343S.
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7. Zemel MB et al. Dairy augmentation of total and central fat loss in obese subjects. Int J Obes 2005;29:391-397.
8. Mozaffarian D, Hao T, Rimm E.B., Willet W.C., Hu F.B. Changes in diet and lifestyle and long-term weight gain in women and men. N Engl J Med. 2011;364(25):2392-2404.
9. Tremblay A., Gilbert J.A. Milk products, insulin resistance syndrome and type 2 diabetes. J Am Coll Nutr. 2009, Supp 1: 91S-102S.
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