Why You Should Ditch Milk When Trying to Lose Fat

Ever since I started my personal training business, my clients always want to know why I ask them to get rid of dairy when they want to lose fat. When I tell them the reasons, people usually accept what I tell them (or pretend to). Now I have no problem with people not taking things at face value, especially with all of the fad diets and snake-oil salesmen out there. One new client of mine wanted to know a bit more: After all, the glycemic index of milk is so low, what the big deal?

Here's my response: While the glycemic index is an excellent measure of how foods affect blood sugar, it isn't the only measure we need to look at; there's also the insulin index. Unfortunately the scientific community never seemed to get too excited about the insulin index. My guess is that there is a common assumption that all foods cause an insulin spike proportional to its glycemic index.

Unfortunately that's not the case!

There are two key studies showing that the low glycemic index of dairy does not correlate with a low insulin response. _(1,2) In fact, the insulin response is quite high! One study found that it was similar to white bread! ₍₁₎ There are actually quite a few studies showing the same effect regarding insulin, but these are the two most recent that I found.

While these studies both have small sample sizes, large groups of people are generally not used when measuring blood glucose/insulin responses in nutrition studies because the vast majority of healthy humans(i.e. people without diabetes, metabolic syndrome, etc.) have the same GI/Insulin responses to the same foods. While this reasoning isn't perfect, and any study would benefit from a large sample, the results are still considered to be valid. Now of course there are quite a few large population studies dealing with the incidence of Type II Diabetes Mellitus (or insulin resistance or metabolic syndrome) and dairy consumption with conflicting results. Many show a lowering of the risk for diabetes with those who consume dairy and some show the opposite. Obviously correlation doesn't equal causation - i.e. just because two things are related, doesn't mean that they caused each other. The problem with these large studies is there are too many other variables to deal with. They don't account for: the activity level of the participants, what kind/quantity of dairy are they consuming, what other foods they're eating, etc.

The other issue with milk  is that it does contain carbohydrates (not a bad thing in itself), and high levels of the amino acid leucine (also not a bad thing) which is known to be insulinotropic (i.e. - produces and insulin spike in the body). When insulinotropic amino acids such as leucine are mixed with carbohydrates there is a greater insulin response in the body than if you only consumed one or the other._(3,4)

You may not like to hear it, but skim milk is the worst kind of dairy you can consume while dieting; there's no fat to slow down the absorption of amino acids and carbohydrates. This is why all of the current research on repairing muscle breakdown in athletes has centered around carbohydrate + amino acid mixes. For a lean highly competitive athlete it may be beneficial to use the insulin spike in skim milk, or a sports drink, to shuttle nutrients to skeletal muscle as quickly as possible. But...

The implication for someone with too much bodyfat is that it just contributes to what may be an already growing level of insulin resistance! In addition to these studies there are a few things that I want to offer in regard to dairy consumption:

1. My client's diets are ALWAYS context based - as you become leaner, you can reintroduce dairy (although most people do better with none)
2. You don't need dairy to get calcium - you can get more than enough from leafy greens, which have the highest density of calcium/kcal (based on the USDA food database)
3. My lean clients (under 12% bodyfat for men and under 20% for women) in some instances consume dairy without any problems.
4. I consume dairy - mainly yogurt for the beneficial bacteria. So I'm not 100% "anti-dairy."

Remember that there's no one-size-fits all diet. I've got clients that can consume plenty of milk and carbohydrates without gaining an ounce of fat. If I was on that diet (as I was when I was younger) I'd put on fat pretty fast (as I have in the past)!

References:

1. Östman EM, Elmståhl HGML, and Björck IME. Inconsistency between glycemic and insulinemic responses to regular and fermented milk products. Am J Clin Nutr 2001; 74:96-100
2. Hoyt G, Hickey MS, Cordain L. Dissociation of the glycaemic and insulinaemic responses to whole and skimmed milk. Br J Nutr 2005; 93:175–177
3. Van Loon LJ, Saris WH, Kruikshoop M, et al. Maximizing postexercise muscle glycogen synthesis: carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures. Am J Clin Nutr. 2000; 72(1):106-11.
4. Manders RJ, Koopman R, Sluijsmans WE, et al. Co-Ingestion of a Protein Hydrolysate with or without Additional Leucine Effectively Reduces Postprandial Blood Glucose Excursions in Type 2 Diabetic Men. J. Nutr. 2006; 136:1294-1299

Milk Man photo by: bobster1985 Milk Ad photo by: flattop341