Mmmmm…milk!
Body proteins are good. You can’t blame them for making you fat. It’s adipose tissue making you fat. That’s what you want to lose when you lose weight, not body proteins.
I wrote recently about a vague “milk diet.” I sought details and found a few in the reference below. The authors write like there’s only one milk diet; I’m skeptical. In fact, at my prior post the milk diet was “a variable combination of full cream or semi-skimmed milk and unsweetened yoghurt.” The study under the microscope today used milk only, probably whole milk.
This was a frustrating study to review. The experimental protocol is complicated, the researchers altered way too many variables, and didn’t hint at how how much weight the dieters lost until the last sentence of the research report. Oh, sure, they gave rates of weight loss during days 2–4, days 1–13, days 13–22, weeks 4–13, and in week 24. But I refuse to calculate total weight loss over those time frames for four different experimental groups.
The goal of the authors was to determine the composition of weight loss on two different very low calorie diets (VLCDs). Would there be differences in fat loss and lean tissue loss? Lean tissue would include muscle, organs, bone, water, etc. Lean tissue is also called fat-free mass. Remember, that’s not the tissue you want to lose when you’re trying to lose excess weight. So measurement of nitrogen loss, a surrogate for protein and lean tissue loss, was the major focus of the study. How do you gauge nitrogen loss? You measure it in urine and feces of the inmates in a hospital metabolic ward.
When I was researching the literature in preparation for writing my first edition of Advanced Mediterranean Diet, I remember reading many studies of very low calorie diets (VLCDs). Offhand, what I remember is that they’re potentially dangerous, compliance is poor, symptomatic gallstones are more common, and they’re only a short-term “solution” because rapid weight regain is a huge problem. VLCDs typically provide 200–800 calories per day.
How Was the Study Done?
All research subjects were women in England. Metabolically healthy except for obesity. Seventeen of the original 22 completed the study. Average age was 33 (range 20–50), average BMI 42, average weight 115 kg (253 lb). They were randomized to eat one of two very low calorie diets:
- Cambridge Diet: 330 cals/day, 33 g protein, 42 g carbohydrate, 3 g fat, plus vitamins and minerals specified in the article
- Milk Diet: 1,200 mls (41 fl oz) of milk daily (780 cals). The milk provided 46 g protein, 56 g carbohydrate, and 46 g fat. Plus supplementation with 60 mg iron, 750 micrograms vitamin A, 7.5 micrograms vitamin D, 1 mg thiamine, 0.5 mg riboflavin, 7.5 mg niacin, 15 mg vitamin C
Unclear whether this milk was from cows, goats, sheep, water buffalo, or yaks. Unclear whether full fat, skim, or some % reduced fat. I’ll assume they used cow milk. Whole milk from a cow is 3.25% fat. Five cups a day (1200 ml) would provide 730 calories, 40 g protein, 65 g carbohydrate, and 40 g fat. The iron, thiamine, and riboflavin in this much milk is very similar to those items used in the Milk Diet above. I got too bored to check the other micronutrients. The point being, if you wanted to emulate the Milk Diet above, drinking 5 cups (1200 ml) of whole milk daily plus a vitamin supplement (and iron?) would get you in the ballpark.
Nor do the researchers describe the Cambridge Diet. Best I can tell, in 1986 it was a commercial diet composed of powder mix, meal bars, and liquid meals. It’s still available, no doubt in different formulations.
Five women in each group agreed to have their jaws wired shut. Wow. This is how they came up with the aforementioned four experiments groups: Cambridge or Milk Diet, jaws wired or not.
The first three weeks were in an inpatient metabolic ward, the next 20 weeks in the outpatient setting, and a final week back in the metabolic ward. I’ve simplified it a bit so you don’t get too lost in the weeds.
All dieters were offered £60 if they completed the entire 24-week protocol.
Results
- From the last sentence of the report, it looks like the Cambridge Dieters lost 21.9 kg (48 lb) and Milk Dieters lost 17.9 kg (39 lb), not a statistically significant difference between the two.
- No patient had to withdraw from the trial due to side effects.
- “Tests of vitamin status showed little of significance.”
- No difference between the diets in terms of hemoglobin, plasma urea, sodium, potassium, triglycerides, cholesterol, glucose, and glucose tolerance test, and “the values were almost all within the normal ranges.”
- “It is concluded that the Cambridge Diet (330 kcal) causes greater N loss [body protein loss] in relation to weight loss than the milk diet (800 kcal)….”
- “Since we have strong reason to doubt that the patients were strictly observing the prescribed diet as outpatients it is dangerous to draw conclusions about the effects of these diets on weight loss and body composition. The most that can be said is that there is no significant difference between the weight loss observed among those who were trying to keep to Cambridge Diet and those who were trying to keep to milk. However, those who had their jaws wired lost significant more weight than those who did not.”
Concluding Thoughts
After the start of this trial, a UK government report suggested that VLCDs should provide at least 500 cals/day and 50 g protein for men, and 400 cals/day and 40 g protein for women. The Cambridge Diet was reformulated to comply with the guidelines.
Can you imagine living only on five cups of milk a day plus a vitamin supplement for 20+ weeks? I gotta admit I’m sorta tempted to try it, but not for 20 weeks. One of my problems with prolonged liquid diets is: what effect does that have on your teeth? We have teeth to chew. Do teeth shift out of place if not used as designed? I’ve never seen it discussed in the scientific literature.
Did nutrient deficiencies “force” dieters to be noncompliant. I don’t know. Sometimes we may need to trust our bodies to help us make the right dietary decisions.
I’ve only reviewed two milk diet studies in these pages. Not many study subjects involved. Nevertheless, at first blush, it looks like a milk diet is relatively safe and effective over several months in otherwise healthy folks. If you were to do it, I’d get the blessing of your personal physician, and probably take a vitamin supplement daily. I bet only menstruating women need an iron supplement.
Sometimes I think diets with too much variety are harder to stick with. Too much temptation. The simplicity of a milk diet appeals to me. Five cups a day. That’s it, nothing else. Don’t even think about it.
Many folks on a weight-loss journey hit a “plateau phase” where they’ve stopped losing weight but are still far from goal. I wonder if a temporary milk diet—one or two months?—is a good option for getting back on track.
Steve Parker, M.D.
Reference: Garrow, J.S., et al. Inpatient-Outpatient Randomized Comparison of Cambridge Diet Versus Milk Diet in 17 Obese Women Over 24 Weeks. International Journal of Obesity (1989) vol. 13, pages 521-529.
