I've heard this refrain countless times:

"Well, that diet and weight loss study used overweight and obese subjects and therefore has no relevance to folks like us i.e., people who exercise, are in tip top shape, love taking selfies, and in our spare time are scientists, or least stayed at a Holiday Inn Express."

On the surface, this particular criticism of studies dealing with diets and weight loss seem plausible. True, they use fat subjects for these studies, but for chrissakes, if you're looking at the effects of diet on fat loss or weight loss, then doesn't it make sense to use folks with fat to lose? Doing a diet and weight loss study on lean people would be like looking at the effects of drinking water on your pet goldfish, so of course you use folks with a spare tire that's reminiscent of a Cinnabon!

Now do these studies paint a crystal clear picture of what strategies are best regarding diets and body composition? Yes and no. And herein lies the conundrum. It reminds me of the famous quote from Winston Churchill and his description of the former Soviet Union: "...it's a riddle, wrapped in a mystery, inside an enigma." That describes perfectly the diet category.

Eventually someone you might remember named Ronald Reagan figured out the Soviet Union and helped topple it like dominoes on a string. In accordance with that, I'll try my best to give you a Reaganesque explanation of diets and hopefully give you some practical knowledge that you can take home and apply to yourself or your fat aunt.

If you were to randomly sample 100 fat people – oops, I mean 100 lean, beautiful people, who want to lose 0.005 mg of fat – what diet would you put them on? A ketogenic diet or a more "balanced" 41:34:17 diet (% each of CHO, Fat, and PRO)? For the sake of clarity, we'll call the latter diet a traditional diet.

Let's look at such a study (sorry to disappoint you, but this study actually used untrained overweight women who wanted to lose more than 0.005 mg of fat). Check out what these women ate for the duration of the study:

Table 2

This was basically a 10-week long study in which these women resistance-trained in combination with either a regular diet (Ex) or a low carbohydrate, ketogenic diet (Lc+Ex). So which worked better? Well, it depends on what you want. Check out the figure below from the study published in Nutrition & Metabolism (1):

Change in kilograms

Which group lost the most body weight and fat? Clearly it was the LC + Ex group (i.e., ketogenic diet). But which group gained the most LBM? Clearly it was the Ex group (i.e., 40:30:30 diet). But that's only part of the picture.

If you look at INDIVIDUAL data points, the picture becomes a bit clearer (or muddled, depending on your pre-conceived notions). Below are the individual data points. God, I hope you paid attention during your "Introduction to Statistics" class in college. Reading this graph is quite simple, actually, although the average college student would say it's as hard as twerking on a surfboard.

Fat Mass Change

You see the blue dots? That's the ketogenic diet group (individual data points). The red diamonds represent individual data points for the traditional diet group. Pay attention now while I walk you through this.

First look at the bottom right blue arrow pointing to the blue dot. That person was on the ketogenic diet. She lost 8 kg of fat while gaining about 3.5 kg of lean body mass. Shazam, that's pretty frickin' impressive!

Okay. Now check out the bottom left green arrow pointing to the blue dot. That person was also on a ketogenic diet. She lost 10.5 kg of fat (wow!), but she also lost a little over a kg of lean body mass. In fact, if you look at all the blue dots to the left of the y-axis, 4 subjects on the ketogenic diet lost LBM. Now you know that ain't good.

Now look at the red arrow at the top right pointing to the red diamond. This person was on the traditional diet. She gained over 4 kg of LBM but didn't lose any fat. In fact, most of the traditional diet people gained LBM and at most lost 2 kg of fat. And last but not least, look at the black arrow on the top left pointing to the red diamond. This sorry subject not only lost LBM but gained fat! WTF? Imagine that. You volunteer for a diet and exercise study and you get fatter and lose muscle. I think I'd go home and eat a bucket of Oreos and watch the OWN network!

So according to this one study, which diet is better? In general, if the goal is to lose body fat, then a ketogenic diet approach is best. If the goal is to gain LBM, a more "balanced" diet is likely better. But you can see that 50% of the subjects on the ketogenic diet lost LBM, whereas the traditional diet group didn't lose much fat at all. The subject who did the very best, however, was on the ketogenic diet.

Yep, you've finally lost that muffin top, or most of it anyhow. So which diet approach should you follow to maintain that weight loss?

A group of researchers brought together some folks who, after achieving a 10% to 15% weight loss, were then put on one of 3 different maintenance diets: an isocaloric low-fat diet (60% of energy from carbohydrate, 20% from fat, 20% from protein; high glycemic load), low-glycemic index diet (40% from carbohydrate, 40% from fat, and 20% from protein; moderate glycemic load), and a very low-carbohydrate diet (10% from carbohydrate, 60% from fat, and 30% from protein; low glycemic load) in random order, each for 4 weeks.

They looked at REE or resting energy expenditure (i.e., metabolic rate) in these subjects. Guess which diet was best at maintaining REE? In general, the very low carbohydrate diet was best, followed by the low-GI diet, and last and least, the low-fat diet. So in general, the lower carb diet wins again (2).

But a closer examination of the individual data points shows that there was a subset of people who did much better on the low-GI diet. And egad, there were even folks who did better on the low-fat diet! Dean Ornish must be smiling.

So what's the bottom line?

  1. In general, the best diet for promoting fat loss is a very low carbohydrate, ketogenic diet.
  2. In general, the best diet for promoting gains in LBM while losing a modicum fat is one higher in carbs and protein.
  3. In general, I'd suggest you try a balanced approach at first (for example, a 40:30:30 approach) and then tweak (not twerk) the diet from there.
  4. Try a "diet" for 4-8 weeks at most, and then switch it out to another approach.
  5. Treat diet the same way you treat training. You don't train the exact same way every week of the year, do you? Of course not.
  6. You can't go wrong eating a boatload of protein daily. And you can't go wrong eating many meals throughout the day (3).
  1. Jabekk PT, Moe IA, Meen HD, Tomten SE, Hostmark AT: Resistance training in overweight women on a ketogenic diet conserved lean body mass while reducing body fat. Nutr Metab (Lond) 2010, 7:17.
  2. Ebbeling CB, Swain JF, Feldman HA, Wong WW, Hachey DL, Garcia-Lago E, Ludwig DS: Effects of dietary composition on energy expenditure during weight-loss maintenance. JAMA 2012, 307:2627-2634.
  3. Arciero PJ, Ormsbee MJ, Gentile CL, Nindl BC, Brestoff JR, Ruby M: Increased protein intake and meal frequency reduces abdominal fat during energy balance and energy deficit. Obesity (Silver Spring) 2013, 21:1357-1366.
Dr. Jose Antonio earned his Ph.D. at the University of Texas Southwestern Medical Center. He currently teaches skeletal muscle physiology at the University of Texas, Arlington, serves as a consultant for fitness/nutrition companies, and writes both scientific and popular press articles on exercise, fitness, and nutrition.