Introduction

It seems like everyone is banting for weight loss these days. Low carbohydrate (LC) diets are promoted as a means for weight loss and reducing body fat. As a qualified dietitian, however, it is important for me to take a look not at media anecdotes, but at the scientific literature first and foremost. It may in fact be time for the health industry to recognize the potential role of LC diets in certain cases. In this article, I will focus on the impact of banting for weight loss.

In the literature, LC diets are not often well defined. Here are the definitions from Feinman et al (2014):

  1. Very Low Carbohydrate Ketogenic Diet (VLCKD): 20–50g/day or <10% of a 2000kcal diet (with or without ketosis)
  2. Low Carbohydrate Diet: <130g/day or <26% of total energy intake
  3. Moderate Carbohydrate Diet: 26-45% of total energy[1]

 

Fat vs Muscle Loss

When you are losing weight on a diet, preferrably we want that weight to be fat and not muscle tissue.[2] It has been shown that muscle mass is preserved more in weight loss on a low carbohydrate diet that on a low fat (LF) diet.[2] This means that the weight lost was in fact mostly fat.

 

Short Term vs Long Term Weight Loss

It does appear that weight loss on a LC diet occurs to a great extent initially (in the first 6 months), and then appears to taper off on longer term use (greater than 6 months). It has been shown by many studies that overweight and obese individuals lose more weight on a LC diet than on a low fat diet.[3,4,5,6,7,8,9,10] One study also found that people using a LC diet are more likely to stick to the diet than those following a LF diet, so this could be part of the reason why the diet achieves such success.[7]

One large meta-analysis (where the results from many studies are analyzed together) examining short term LC diet use also showed that a LC diet is a feasible alternative to a LF diet for inducing weight loss.[11] However, the studies included in the meta-analysis were VLCKD with daily carbohydrate intakes of 30g or less.

 

Long Term Banting for Weight Loss

We can conclusively say that a LC diet can achieve weight loss in overweight and obese people in the short term. There are conflicting results when looking at the effects of longer term use of LC diets on weight loss. A large meta-analysis earlier this year, conducted in South Africa, showed that weight loss results on a LC diet are insignificant when compared to results on a LF diet.[12] This contrasted with other previous studies where greater weight loss was still achieved with LC diet use.[13]

When you take a look at the South African meta-analysis however, many of the studies included do not qualify for the title of LC as the daily carbohydrate intake was >130g/d.[14,15,16,17,18,19,20] This may render their conclusions meaningless (in a sense).

 

Long Term Banting for Weight Loss With Support

The bridge between conflicting results may lie in the concurrent use of dietary guidance, support and other lifestyle interventions. It has been shown in the literature that neither dietary fat nor carbohydrate intake influenced weight loss when combined with lifestyle intervention.[21] This meant basically that both a LF diet and LC diet were effective in reducing weight, as long as the individual had a supportive environment.

The LC diet group did however have greater HDL cholesterol concentrations than the LF diet group at the end of the 2 year period, so there are potential cardioprotective effects.[21]

 

Potential Side Effects

Some common side effects in the initial period (1-3 weeks) of LC diet use:

  1. Fatigue
  2. Headaches
  3. Weakness [22]

These effects are common in feelings of “starvation” because your body is adapting to the lack of glucose in the blood, however they tend to decrease or disappear once adaptation has occurred (around 2-3weeks of use).

In longer term use of a LC diet there appears to be an increased risk for deficiencies in vitamins and minerals, as well as a decreased fibre intake.[23] These need not occur if you include nutrient-rich vegetables, berries, nuts and seeds, and organic meats in your diet. When improperly executed, a LC diet may include a high dietary protein intake which increases the risk for renal dysfunction (in pre-disposed individuals), as well as altered water and electrolyte balance.[23]

There are potential concerns over skeletal health on a LC diet as results from the literature are conflicting. There is evidence to support increased risk for osteopenia and osteoporosis on a LC diet, as well as evidence to contradict this.[24] Further research is needed in this area!

LC diet use has been shown to increase HDL cholesterol and decrease serum triglyerides, both of which are extremely beneficial to reduce heart disease risk![11] We also know that it may increase your total cholesterol and LDL cholesterol, but these are not necessarily valid indicators of cardiac risk.[11]

 

Final Points

Banting for weight loss can be successful according to the literature (as well as testimonies from many people who have tried the diet). The research supports the use of banting for weight loss in overweight and obese people. Unfortunately we do not know the long term implications beyond 2 years in terms of health. However the literature seems to show that there are relatively low risks in terms of using LC diets. It seems paramount, however, that you need continued support to ensure the diet (and weight loss) is sustained.

 

References

  1. Feinman RD, Pogozelski WK, Astrup A, Bernstein RK, Fine EJ, Westman EC, Accurso A, Frasetto L, McFarlane S, Nielsen JV, Krarup T, Gower BA, Saslow L, Roth KS, Vernon MC, Volek JS, Wilshire GB, Dahlqvist A, Sundberg R, Childers A, Morrison K, Manninen AH, Dashti H, Wood RJ, Wortman J, Worm N. Dietary carbohydrate restriction as the first approach in diabetes management. Critical review and evidence base. J Nutr. Epub ahead of print. 2014 Jul 16. doi: 10.1016/j.nut.2014.06.011.
  2. Hoffer LJ, Bistrian BR, Young VR, Blackburn GL, Matthews DE. Metabolic effects of very low calorie weight reduction diets. J Clin Invest. Mar 1984; 73(3): 750–758.
  3. Samaha FF, Igbal N, Seshadri P, Chicano KL, Daily DA, McGrory J, Wiliams T, Williams M, Gracely J, Stern L. A low-carbohydrate as compared with a low-fat diet in severe obesity. N Engl J Med. 2003 May 22;348(21):2074-81.
  4. Sondike, S B., Copperman, N., Jacobson, M S. (2003). Effects of a low-carbohydrate diet on weight loss and cardiovascular risk factor in overweight adolescents. J Pediatr. 2003 Mar;142(3):253-8.
  5. Aude YW, Agatston AS, Lopez-Jimenez F, Lieberman EH, Marie A, et al. The national cholesterol education program diet vs a diet lower in carbohydrates and higher in protein and monounsaturated fat: a randomized trial. Arch Intern Med. 2004 Oct 25;164: 2141–2146.
  6. Volek JS, Sharman MJ, Gómez AL, Judelson DA, Rubin MR, Watson G, Sokmen B, Silvestre R, French DN, Kraemer WJ. Comparison of energy-restricted very low-carbohydrate and low-fat diets on weight loss and body composition in overweight men and women. Nutr Metab (Lond). 2004 Nov 8;1(1):13.
  7. Yancy WS, Olsen MK, Guyton JR, Bakst RP, Westman EC. A low-carbohydrate, ketogenic diet versus a low-fat diet to treat obesity and hyperlipidemia, a randomized, controlled trial. Ann Intern Med. 2004 May 18;140(10):769-77.
  8. Krebs NF, Gao D, Gralla J, Collins JS, Johnson SJ. Efficacy and safety of a high protein, low carbohydrate diet for weight loss in severely obese adolescents. J Pediatr. 2010 Aug;157(2):252-8.
  9. Dyson PA, Beatty S, Matthews DR. A low-carbohydrate diet is more effective in reducing body weight than healthy eating in both diabetic and non-diabetic subjects. Diabet Med. 2007 Dec;24(12):1430-5.
  10. Volek JS, Phinney SD, Forsythe CE, Quann EE, Wood RJ, Puglisi MJ, Kraemer WJ, Bibus DM, Luz Fernandez M, Feinman RD. Carbohydrate restriction has a more favourable impact on the metabolic syndrome than a low fat diet. Lipids. 2009 Apr;44(4):297-309.
  11. Nordman AJ, Nordman A, Briel M, Keller U, Yancy WS, Brehm BJ, Bucher HC. Effects of low-carbohydrate vs low-fat Diets on weight loss and cardiovascular risk factors. Arch Intern Med. 2006 Feb 13;166(3):285-93.
  12. Naude CE, Schoonees A, Senekal M, Young T, Garner P, Volmink J. Low carbohydrate versus isoenergetic balanced diets for reducing weight and cardiovascular risk: a systematic review and meta-analysis. PloS One. 2014 Jul 9; 1-30.
  13. Gardner CD, Kiazand A, Alhassan S, et al. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women. The A to Z Weight Loss Study: A randomized trial. JAMA 2007;297(9):969-977.
  14. De Luis DA, Sagrado MG, Conde R, Aller R, Izaola O. The effects of two different hypocaloric diets on glucagon-like peptide 1 in obese adults, relation with insulin response after weight loss. J Diabetes Complications 2009;23(4):239-243.
  15. De Luis DA, Aller R, Izaola O, et al. Evaluation of weight loss and adipocytokines levels after two hypocaloric diets with different macronutrient distribution in obese subjects with rs9939609 gene variant. Diabetes Metab Res Rev 2012;28(8):663-668.
  16. Farnsworth E, Luscombe ND, Noakes M, Wittert G, Argyiou E, Clifton PM. Effect of a high-protein, energy-restricted diet on body composition, glycemic control, and lipid concentrations in overweight and obese hyperinsulinemic men and women. Am J Clin Nutr 2003;78(1):31-39.
  17. Lasker DAW, Evans EM, Layman DK. Moderate carbohydrate, moderate protein weight loss diet reduces cardiovascular disease risk compared to high carbohydrate, low protein diet in obese adults: A randomized clinical trial. Nutr Metab 2008;5:30.
  18. Layman DK, Evans EM, Erickson D, et al. A moderate-protein diet produces sustained weight loss and long-term changes in body composition and blood lipids in obese adults. J Nutr 2009;139(3):514-521.
  19. Luscombe ND, Clifton PM, Noakes M, Farnsworth E, Wittert G. Effect of a high-protein, energy-restricted diet on weight loss and energy expenditure after weight stabilization in hyperinsulinemic subjects. Int J Obes Relat Metab Disord 2003;27(5):582-590.
  20. Wycherley TP, Brinkworth GD, Clifton PM, Noakes M. Comparison of the effects of 52 weeks weight loss with either a high-protein or high-carbohydrate diet on body composition and cardiometabolic risk factors in overweight and obese males. Nutr Diabetes 2012;2:e40.
  21. Gary D. Foster, Holly R. Wyatt, James O. Hill, Angela P. Makris, Diane L. Rosenbaum, Carrie Brill, Richard I. Stein, B. Selma Mohammed, Bernard Miller, Daniel J. Rader, Babette Zemel, Thomas A. Wadden, Thomas Tenhave, Craig W. Newcomb, Samuel Klein. Weight and metabolic outcomes after 2 years on a low-carbohydrate versus low-fat diet: a randomized trial. Ann Intern Med. 2010 Aug 3; 153(3): 147–157.
  22. Freedman MR, King J, Kennedy E. Popular diets: a scientific review. Obes Res 2001;9:S1:1S-40S.